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| -rw-r--r-- | Documentation/block/bfq-iosched.txt | 517 | ||||
| -rw-r--r-- | block/Kconfig.iosched | 11 | ||||
| -rw-r--r-- | block/Makefile | 1 | ||||
| -rw-r--r-- | block/bfq-iosched.c | 4166 |
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diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX index e55103ace382..8d55b4bbb5e2 100644 --- a/Documentation/block/00-INDEX +++ b/Documentation/block/00-INDEX @@ -1,5 +1,7 @@ 00-INDEX - This file +bfq-iosched.txt + - BFQ IO scheduler and its tunables biodoc.txt - Notes on the Generic Block Layer Rewrite in Linux 2.5 biovecs.txt diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt new file mode 100644 index 000000000000..cbf85f6f1fd8 --- /dev/null +++ b/Documentation/block/bfq-iosched.txt @@ -0,0 +1,517 @@ +BFQ (Budget Fair Queueing) +========================== + +BFQ is a proportional-share I/O scheduler, with some extra +low-latency capabilities. In addition to cgroups support (blkio or io +controllers), BFQ's main features are: +- BFQ guarantees a high system and application responsiveness, and a + low latency for time-sensitive applications, such as audio or video + players; +- BFQ distributes bandwidth, and not just time, among processes or + groups (switching back to time distribution when needed to keep + throughput high). + +On average CPUs, the current version of BFQ can handle devices +performing at most ~30K IOPS; at most ~50 KIOPS on faster CPUs. As a +reference, 30-50 KIOPS correspond to very high bandwidths with +sequential I/O (e.g., 8-12 GB/s if I/O requests are 256 KB large), and +to 120-200 MB/s with 4KB random I/O. BFQ has not yet been tested on +multi-queue devices. + +The table of contents follow. Impatients can just jump to Section 3. + +CONTENTS + +1. When may BFQ be useful? + 1-1 Personal systems + 1-2 Server systems +2. How does BFQ work? +3. What are BFQ's tunable? +4. BFQ group scheduling + 4-1 Service guarantees provided + 4-2 Interface + +1. When may BFQ be useful? +========================== + +BFQ provides the following benefits on personal and server systems. + +1-1 Personal systems +-------------------- + +Low latency for interactive applications + +Regardless of the actual background workload, BFQ guarantees that, for +interactive tasks, the storage device is virtually as responsive as if +it was idle. For example, even if one or more of the following +background workloads are being executed: +- one or more large files are being read, written or copied, +- a tree of source files is being compiled, +- one or more virtual machines are performing I/O, +- a software update is in progress, +- indexing daemons are scanning filesystems and updating their + databases, +starting an application or loading a file from within an application +takes about the same time as if the storage device was idle. As a +comparison, with CFQ, NOOP or DEADLINE, and in the same conditions, +applications experience high latencies, or even become unresponsive +until the background workload terminates (also on SSDs). + +Low latency for soft real-time applications + +Also soft real-time applications, such as audio and video +players/streamers, enjoy a low latency and a low drop rate, regardless +of the background I/O workload. As a consequence, these applications +do not suffer from almost any glitch due to the background workload. + +Higher speed for code-development tasks + +If some additional workload happens to be executed in parallel, then +BFQ executes the I/O-related components of typical code-development +tasks (compilation, checkout, merge, ...) much more quickly than CFQ, +NOOP or DEADLINE. + +High throughput + +On hard disks, BFQ achieves up to 30% higher throughput than CFQ, and +up to 150% higher throughput than DEADLINE and NOOP, with all the +sequential workloads considered in our tests. With random workloads, +and with all the workloads on flash-based devices, BFQ achieves, +instead, about the same throughput as the other schedulers. + +Strong fairness, bandwidth and delay guarantees + +BFQ distributes the device throughput, and not just the device time, +among I/O-bound applications in proportion their weights, with any +workload and regardless of the device parameters. From these bandwidth +guarantees, it is possible to compute tight per-I/O-request delay +guarantees by a simple formula. If not configured for strict service +guarantees, BFQ switches to time-based resource sharing (only) for +applications that would otherwise cause a throughput loss. + +1-2 Server systems +------------------ + +Most benefits for server systems follow from the same service +properties as above. In particular, regardless of whether additional, +possibly heavy workloads are being served, BFQ guarantees: + +. audio and video-streaming with zero or very low jitter and drop + rate; + +. fast retrieval of WEB pages and embedded objects; + +. real-time recording of data in live-dumping applications (e.g., + packet logging); + +. responsiveness in local and remote access to a server. + + +2. How does BFQ work? +===================== + +BFQ is a proportional-share I/O scheduler, whose general structure, +plus a lot of code, are borrowed from CFQ. + +- Each process doing I/O on a device is associated with a weight and a + (bfq_)queue. + +- BFQ grants exclusive access to the device, for a while, to one queue + (process) at a time, and implements this service model by + associating every queue with a budget, measured in number of + sectors. + + - After a queue is granted access to the device, the budget of the + queue is decremented, on each request dispatch, by the size of the + request. + + - The in-service queue is expired, i.e., its service is suspended, + only if one of the following events occurs: 1) the queue finishes + its budget, 2) the queue empties, 3) a "budget timeout" fires. + + - The budget timeout prevents processes doing random I/O from + holding the device for too long and dramatically reducing + throughput. + + - Actually, as in CFQ, a queue associated with a process issuing + sync requests may not be expired immediately when it empties. In + contrast, BFQ may idle the device for a short time interval, + giving the process the chance to go on being served if it issues + a new request in time. Device idling typically boosts the + throughput on rotational devices, if processes do synchronous + and sequential I/O. In addition, under BFQ, device idling is + also instrumental in guaranteeing the desired throughput + fraction to processes issuing sync requests (see the description + of the slice_idle tunable in this document, or [1, 2], for more + details). + + - With respect to idling for service guarantees, if several + processes are competing for the device at the same time, but + all processes (and groups, after the following commit) have + the same weight, then BFQ guarantees the expected throughput + distribution without ever idling the device. Throughput is + thus as high as possible in this common scenario. + + - If low-latency mode is enabled (default configuration), BFQ + executes some special heuristics to detect interactive and soft + real-time applications (e.g., video or audio players/streamers), + and to reduce their latency. The most important action taken to + achieve this goal is to give to the queues associated with these + applications more than their fair share of the device + throughput. For brevity, we call just "weight-raising" the whole + sets of actions taken by BFQ to privilege these queues. In + particular, BFQ provides a milder form of weight-raising for + interactive applications, and a stronger form for soft real-time + applications. + + - BFQ automatically deactivates idling for queues born in a burst of + queue creations. In fact, these queues are usually associated with + the processes of applications and services that benefit mostly + from a high throughput. Examples are systemd during boot, or git + grep. + + - As CFQ, BFQ merges queues performing interleaved I/O, i.e., + performing random I/O that becomes mostly sequential if + merged. Differently from CFQ, BFQ achieves this goal with a more + reactive mechanism, called Early Queue Merge (EQM). EQM is so + responsive in detecting interleaved I/O (cooperating processes), + that it enables BFQ to achieve a high throughput, by queue + merging, even for queues for which CFQ needs a different + mechanism, preemption, to get a high throughput. As such EQM is a + unified mechanism to achieve a high throughput with interleaved + I/O. + + - Queues are scheduled according to a variant of WF2Q+, named + B-WF2Q+, and implemented using an augmented rb-tree to preserve an + O(log N) overall complexity. See [2] for more details. B-WF2Q+ is + also ready for hierarchical scheduling. However, for a cleaner + logical breakdown, the code that enables and completes + hierarchical support is provided in the next commit, which focuses + exactly on this feature. + + - B-WF2Q+ guarantees a tight deviation with respect to an ideal, + perfectly fair, and smooth service. In particular, B-WF2Q+ + guarantees that each queue receives a fraction of the device + throughput proportional to its weight, even if the throughput + fluctuates, and regardless of: the device parameters, the current + workload and the budgets assigned to the queue. + + - The last, budget-independence, property (although probably + counterintuitive in the first place) is definitely beneficial, for + the following reasons: + + - First, with any proportional-share scheduler, the maximum + deviation with respect to an ideal service is proportional to + the maximum budget (slice) assigned to queues. As a consequence, + BFQ can keep this deviation tight not only because of the + accurate service of B-WF2Q+, but also because BFQ *does not* + need to assign a larger budget to a queue to let the queue + receive a higher fraction of the device throughput. + + - Second, BFQ is free to choose, for every process (queue), the + budget that best fits the needs of the process, or best + leverages the I/O pattern of the process. In particular, BFQ + updates queue budgets with a simple feedback-loop algorithm that + allows a high throughput to be achieved, while still providing + tight latency guarantees to time-sensitive applications. When + the in-service queue expires, this algorithm computes the next + budget of the queue so as to: + + - Let large budgets be eventually assigned to the queues + associated with I/O-bound applications performing sequential + I/O: in fact, the longer these applications are served once + got access to the device, the higher the throughput is. + + - Let small budgets be eventually assigned to the queues + associated with time-sensitive applications (which typically + perform sporadic and short I/O), because, the smaller the + budget assigned to a queue waiting for service is, the sooner + B-WF2Q+ will serve that queue (Subsec 3.3 in [2]). + +- If several processes are competing for the device at the same time, + but all processes and groups have the same weight, then BFQ + guarantees the expected throughput distribution without ever idling + the device. It uses preemption instead. Throughput is then much + higher in this common scenario. + +- ioprio classes are served in strict priority order, i.e., + lower-priority queues are not served as long as there are + higher-priority queues. Among queues in the same class, the + bandwidth is distributed in proportion to the weight of each + queue. A very thin extra bandwidth is however guaranteed to + the Idle class, to prevent it from starving. + + +3. What are BFQ's tunable? +========================== + +The tunables back_seek-max, back_seek_penalty, fifo_expire_async and +fifo_expire_sync below are the same as in CFQ. Their description is +just copied from that for CFQ. Some considerations in the description +of slice_idle are copied from CFQ too. + +per-process ioprio and weight +----------------------------- + +Unless the cgroups interface is used, weights can be assigned to +processes only indirectly, through I/O priorities, and according to +the relation: weight = (IOPRIO_BE_NR - ioprio) * 10. + +slice_idle +---------- + +This parameter specifies how long BFQ should idle for next I/O +request, when certain sync BFQ queues become empty. By default +slice_idle is a non-zero value. Idling has a double purpose: boosting +throughput and making sure that the desired throughput distribution is +respected (see the description of how BFQ works, and, if needed, the +papers referred there). + +As for throughput, idling can be very helpful on highly seeky media +like single spindle SATA/SAS disks where we can cut down on overall +number of seeks and see improved throughput. + +Setting slice_idle to 0 will remove all the idling on queues and one +should see an overall improved throughput on faster storage devices +like multiple SATA/SAS disks in hardware RAID configuration. + +So depending on storage and workload, it might be useful to set +slice_idle=0. In general for SATA/SAS disks and software RAID of +SATA/SAS disks keeping slice_idle enabled should be useful. For any +configurations where there are multiple spindles behind single LUN +(Host based hardware RAID controller or for storage arrays), setting +slice_idle=0 might end up in better throughput and acceptable +latencies. + +Idling is however necessary to have service guarantees enforced in +case of differentiated weights or differentiated I/O-request lengths. +To see why, suppose that a given BFQ queue A must get several I/O +requests served for each request served for another queue B. Idling +ensures that, if A makes a new I/O request slightly after becoming +empty, then no request of B is dispatched in the middle, and thus A +does not lose the possibility to get more than one request dispatched +before the next request of B is dispatched. Note that idling +guarantees the desired differentiated treatment of queues only in +terms of I/O-request dispatches. To guarantee that the actual service +order then corresponds to the dispatch order, the strict_guarantees +tunable must be set too. + +There is an important flipside for idling: apart from the above cases +where it is beneficial also for throughput, idling can severely impact +throughput. One important case is random workload. Because of this +issue, BFQ tends to avoid idling as much as possible, when it is not +beneficial also for throughput. As a consequence of this behavior, and +of further issues described for the strict_guarantees tunable, +short-term service guarantees may be occasionally violated. And, in +some cases, these guarantees may be more important than guaranteeing +maximum throughput. For example, in video playing/streaming, a very +low drop rate may be more important than maximum throughput. In these +cases, consider setting the strict_guarantees parameter. + +strict_guarantees +----------------- + +If this parameter is set (default: unset), then BFQ + +- always performs idling when the in-service queue becomes empty; + +- forces the device to serve one I/O request at a time, by dispatching a + new request only if there is no outstanding request. + +In the presence of differentiated weights or I/O-request sizes, both +the above conditions are needed to guarantee that every BFQ queue +receives its allotted share of the bandwidth. The first condition is +needed for the reasons explained in the description of the slice_idle +tunable. The second condition is needed because all modern storage +devices reorder internally-queued requests, which may trivially break +the service guarantees enforced by the I/O scheduler. + +Setting strict_guarantees may evidently affect throughput. + +back_seek_max +------------- + +This specifies, given in Kbytes, the maximum "distance" for backward seeking. +The distance is the amount of space from the current head location to the +sectors that are backward in terms of distance. + +This parameter allows the scheduler to anticipate requests in the "backward" +direction and consider them as being the "next" if they are within this +distance from the current head location. + +back_seek_penalty +----------------- + +This parameter is used to compute the cost of backward seeking. If the +backward distance of request is just 1/back_seek_penalty from a "front" +request, then the seeking cost of two requests is considered equivalent. + +So scheduler will not bias toward one or the other request (otherwise scheduler +will bias toward front request). Default value of back_seek_penalty is 2. + +fifo_expire_async +----------------- + +This parameter is used to set the timeout of asynchronous requests. Default +value of this is 248ms. + +fifo_expire_sync +---------------- + +This parameter is used to set the timeout of synchronous requests. Default +value of this is 124ms. In case to favor synchronous requests over asynchronous +one, this value should be decreased relative to fifo_expire_async. + +low_latency +----------- + +This parameter is used to enable/disable BFQ's low latency mode. By +default, low latency mode is enabled. If enabled, interactive and soft +real-time applications are privileged and experience a lower latency, +as explained in more detail in the description of how BFQ works. + +timeout_sync +------------ + +Maximum amount of device time that can be given to a task (queue) once +it has been selected for service. On devices with costly seeks, +increasing this time usually increases maximum throughput. On the +opposite end, increasing this time coarsens the granularity of the +short-term bandwidth and latency guarantees, especially if the +following parameter is set to zero. + +max_budget +---------- + +Maximum amount of service, measured in sectors, that can be provided +to a BFQ queue once it is set in service (of course within the limits +of the above timeout). According to what said in the description of +the algorithm, larger values increase the throughput in proportion to +the percentage of sequential I/O requests issued. The price of larger +values is that they coarsen the granularity of short-term bandwidth +and latency guarantees. + +The default value is 0, which enables auto-tuning: BFQ sets max_budget +to the maximum number of sectors that can be served during +timeout_sync, according to the estimated peak rate. + +weights +------- + +Read-only parameter, used to show the weights of the currently active +BFQ queues. + + +wr_ tunables +------------ + +BFQ exports a few parameters to control/tune the behavior of +low-latency heuristics. + +wr_coeff + +Factor by which the weight of a weight-raised queue is multiplied. If +the queue is deemed soft real-time, then the weight is further +multiplied by an additional, constant factor. + +wr_max_time + +Maximum duration of a weight-raising period for an interactive task +(ms). If set to zero (default value), then this value is computed +automatically, as a function of the peak rate of the device. In any +case, when the value of this parameter is read, it always reports the +current duration, regardless of whether it has been set manually or +computed automatically. + +wr_max_softrt_rate + +Maximum service rate below which a queue is deemed to be associated +with a soft real-time application, and is then weight-raised +accordingly (sectors/sec). + +wr_min_idle_time + +Minimum idle period after which interactive weight-raising may be +reactivated for a queue (in ms). + +wr_rt_max_time + +Maximum weight-raising duration for soft real-time queues (in ms). The +start time from which this duration is considered is automatically +moved forward if the queue is detected to be still soft real-time +before the current soft real-time weight-raising period finishes. + +wr_min_inter_arr_async + +Minimum period between I/O request arrivals after which weight-raising +may be reactivated for an already busy async queue (in ms). + + +4. Group scheduling with BFQ +============================ + +BFQ supports both cgroup-v1 and cgroup-v2 io controllers, namely blkio +and io. In particular, BFQ supports weight-based proportional +share. + +4-1 Service guarantees provided +------------------------------- + +With BFQ, proportional share means true proportional share of the +device bandwidth, according to group weights. For example, a group +with weight 200 gets twice the bandwidth, and not just twice the time, +of a group with weight 100. + +BFQ supports hierarchies (group trees) of any depth. Bandwidth is +distributed among groups and processes in the expected way: for each +group, the children of the group share the whole bandwidth of the +group in proportion to their weights. In particular, this implies +that, for each leaf group, every process of the group receives the +same share of the whole group bandwidth, unless the ioprio of the +process is modified. + +The resource-sharing guarantee for a group may partially or totally +switch from bandwidth to time, if providing bandwidth guarantees to +the group lowers the throughput too much. This switch occurs on a +per-process basis: if a process of a leaf group causes throughput loss +if served in such a way to receive its share of the bandwidth, then +BFQ switches back to just time-based proportional share for that +process. + +4-2 Interface +------------- + +To get proportional sharing of bandwidth with BFQ for a given device, +BFQ must of course be the active scheduler for that device. + +Within each group directory, the names of the files associated with +BFQ-specific cgroup parameters and stats begin with the "bfq." +prefix. So, with cgroups-v1 or cgroups-v2, the full prefix for +BFQ-specific files is "blkio.bfq." or "io.bfq." For example, the group +parameter to set the weight of a group with BFQ is blkio.bfq.weight +or io.bfq.weight. + +Parameters to set +----------------- + +For each group, there is only the following parameter to set. + +weight (namely blkio.bfq.weight or io.bfq-weight): the weight of the +group inside its parent. Available values: 1..10000 (default 100). The +linear mapping between ioprio and weights, described at the beginning +of the tunable section, is still valid, but all weights higher than +IOPRIO_BE_NR*10 are mapped to ioprio 0. + + +[1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O + Scheduler", Proceedings of the First Workshop on Mobile System + Technologies (MST-2015), May 2015. + http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf + +[2] P. Valente and M. Andreolini, "Improving Application + Responsiveness with the BFQ Disk I/O Scheduler", Proceedings of + the 5th Annual International Systems and Storage Conference + (SYSTOR '12), June 2012. + Slightly extended version: + http://algogroup.unimore.it/people/paolo/disk_sched/bfq-v1-suite- + results.pdf diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched index 916e69c68fa4..6fc36027b70e 100644 --- a/block/Kconfig.iosched +++ b/block/Kconfig.iosched @@ -78,6 +78,17 @@ config MQ_IOSCHED_KYBER synchronous writes, it will self-tune queue depths to achieve that goal. +config IOSCHED_BFQ + tristate "BFQ I/O scheduler" + default n + ---help--- + BFQ I/O scheduler for BLK-MQ. BFQ distributes the bandwidth of + of the device among all processes according to their weights, + regardless of the device parameters and with any workload. It + also guarantees a low latency to interactive and soft + real-time applications. Details in + Documentation/block/bfq-iosched.txt + endmenu endif diff --git a/block/Makefile b/block/Makefile index 6146d2eaaeaa..4c1d68cb49dd 100644 --- a/block/Makefile +++ b/block/Makefile @@ -21,6 +21,7 @@ obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o obj-$(CONFIG_MQ_IOSCHED_DEADLINE) += mq-deadline.o obj-$(CONFIG_MQ_IOSCHED_KYBER) += kyber-iosched.o +obj-$(CONFIG_IOSCHED_BFQ) += bfq-iosched.o obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o obj-$(CONFIG_BLK_CMDLINE_PARSER) += cmdline-parser.o diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c new file mode 100644 index 000000000000..c4e7d8db796a --- /dev/null +++ b/block/bfq-iosched.c @@ -0,0 +1,4166 @@ +/* + * Budget Fair Queueing (BFQ) I/O scheduler. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> + * + * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it> + * Paolo Valente <paolo.valente@unimore.it> + * + * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it> + * Arianna Avanzini <avanzini@google.com> + * + * Copyright (C) 2017 Paolo Valente <paolo.valente@linaro.org> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * BFQ is a proportional-share I/O scheduler, with some extra + * low-latency capabilities. BFQ also supports full hierarchical + * scheduling through cgroups. Next paragraphs provide an introduction + * on BFQ inner workings. Details on BFQ benefits, usage and + * limitations can be found in Documentation/block/bfq-iosched.txt. + * + * BFQ is a proportional-share storage-I/O scheduling algorithm based + * on the slice-by-slice service scheme of CFQ. But BFQ assigns + * budgets, measured in number of sectors, to processes instead of + * time slices. The device is not granted to the in-service process + * for a given time slice, but until it has exhausted its assigned + * budget. This change from the time to the service domain enables BFQ + * to distribute the device throughput among processes as desired, + * without any distortion due to throughput fluctuations, or to device + * internal queueing. BFQ uses an ad hoc internal scheduler, called + * B-WF2Q+, to schedule processes according to their budgets. More + * precisely, BFQ schedules queues associated with processes. Each + * process/queue is assigned a user-configurable weight, and B-WF2Q+ + * guarantees that each queue receives a fraction of the throughput + * proportional to its weight. Thanks to the accurate policy of + * B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound + * processes issuing sequential requests (to boost the throughput), + * and yet guarantee a low latency to interactive and soft real-time + * applications. + * + * In particular, to provide these low-latency guarantees, BFQ + * explicitly privileges the I/O of two classes of time-sensitive + * applications: interactive and soft real-time. This feature enables + * BFQ to provide applications in these classes with a very low + * latency. Finally, BFQ also features additional heuristics for + * preserving both a low latency and a high throughput on NCQ-capable, + * rotational or flash-based devices, and to get the job done quickly + * for applications consisting in many I/O-bound processes. + * + * BFQ is described in [1], where also a reference to the initial, more + * theoretical paper on BFQ can be found. The interested reader can find + * in the latter paper full details on the main algorithm, as well as + * formulas of the guarantees and formal proofs of all the properties. + * With respect to the version of BFQ presented in these papers, this + * implementation adds a few more heuristics, such as the one that + * guarantees a low latency to soft real-time applications, and a + * hierarchical extension based on H-WF2Q+. + * + * B-WF2Q+ is based on WF2Q+, which is described in [2], together with + * H-WF2Q+, while the augmented tree used here to implement B-WF2Q+ + * with O(log N) complexity derives from the one introduced with EEVDF + * in [3]. + * + * [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O + * Scheduler", Proceedings of the First Workshop on Mobile System + * Technologies (MST-2015), May 2015. + * http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf + * + * [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing + * Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689, + * Oct 1997. + * + * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz + * + * [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline + * First: A Flexible and Accurate Mechanism for Proportional Share + * Resource Allocation", technical report. + * + * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf + */ +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/blkdev.h> +#include <linux/elevator.h> +#include <linux/ktime.h> +#include <linux/rbtree.h> +#include <linux/ioprio.h> +#include <linux/sbitmap.h> +#include <linux/delay.h> + +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-tag.h" +#include "blk-mq-sched.h" +#include <linux/blktrace_api.h> +#include <linux/hrtimer.h> +#include <linux/blk-cgroup.h> + +#define BFQ_IOPRIO_CLASSES 3 +#define BFQ_CL_IDLE_TIMEOUT (HZ/5) + +#define BFQ_MIN_WEIGHT 1 +#define BFQ_MAX_WEIGHT 1000 +#define BFQ_WEIGHT_CONVERSION_COEFF 10 + +#define BFQ_DEFAULT_QUEUE_IOPRIO 4 + +#define BFQ_DEFAULT_GRP_WEIGHT 10 +#define BFQ_DEFAULT_GRP_IOPRIO 0 +#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE + +struct bfq_entity; + +/** + * struct bfq_service_tree - per ioprio_class service tree. + * + * Each service tree represents a B-WF2Q+ scheduler on its own. Each + * ioprio_class has its own independent scheduler, and so its own + * bfq_service_tree. All the fields are protected by the queue lock + * of the containing bfqd. + */ +struct bfq_service_tree { + /* tree for active entities (i.e., those backlogged) */ + struct rb_root active; + /* tree for idle entities (i.e., not backlogged, with V <= F_i)*/ + struct rb_root idle; + + /* idle entity with minimum F_i */ + struct bfq_entity *first_idle; + /* idle entity with maximum F_i */ + struct bfq_entity *last_idle; + + /* scheduler virtual time */ + u64 vtime; + /* scheduler weight sum; active and idle entities contribute to it */ + unsigned long wsum; +}; + +/** + * struct bfq_sched_data - multi-class scheduler. + * + * bfq_sched_data is the basic scheduler queue. It supports three + * ioprio_classes, and can be used either as a toplevel queue or as + * an intermediate queue on a hierarchical setup. + * @next_in_service points to the active entity of the sched_data + * service trees that will be scheduled next. + * + * The supported ioprio_classes are the same as in CFQ, in descending + * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE. + * Requests from higher priority queues are served before all the + * requests from lower priority queues; among requests of the same + * queue requests are served according to B-WF2Q+. + * All the fields are protected by the queue lock of the containing bfqd. + */ +struct bfq_sched_data { + /* entity in service */ + struct bfq_entity *in_service_entity; + /* head-of-the-line entity in the scheduler */ + struct bfq_entity *next_in_service; + /* array of service trees, one per ioprio_class */ + struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES]; +}; + +/** + * struct bfq_entity - schedulable entity. + * + * A bfq_entity is used to represent a bfq_queue (leaf node in the upper + * level scheduler). Each entity belongs to the sched_data of the parent + * group hierarchy. Non-leaf entities have also their own sched_data, + * stored in @my_sched_data. + * + * Each entity stores independently its priority values; this would + * allow different weights on different devices, but this + * functionality is not exported to userspace by now. Priorities and + * weights are updated lazily, first storing the new values into the + * new_* fields, then setting the @prio_changed flag. As soon as + * there is a transition in the entity state that allows the priority + * update to take place the effective and the requested priority + * values are synchronized. + * + * The weight value is calculated from the ioprio to export the same + * interface as CFQ. When dealing with ``well-behaved'' queues (i.e., + * queues that do not spend too much time to consume their budget + * and have true sequential behavior, and when there are no external + * factors breaking anticipation) the relative weights at each level + * of the hierarchy should be guaranteed. All the fields are + * protected by the queue lock of the containing bfqd. + */ +struct bfq_entity { + /* service_tree member */ + struct rb_node rb_node; + + /* + * flag, true if the entity is on a tree (either the active or + * the idle one of its service_tree). + */ + int on_st; + + /* B-WF2Q+ start and finish timestamps [sectors/weight] */ + u64 start, finish; + + /* tree the entity is enqueued into; %NULL if not on a tree */ + struct rb_root *tree; + + /* + * minimum start time of the (active) subtree rooted at this + * entity; used for O(log N) lookups into active trees + */ + u64 min_start; + + /* amount of service received during the last service slot */ + int service; + + /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */ + int budget; + + /* weight of the queue */ + int weight; + /* next weight if a change is in progress */ + int new_weight; + + /* original weight, used to implement weight boosting */ + int orig_weight; + + /* parent entity, for hierarchical scheduling */ + struct bfq_entity *parent; + + /* + * For non-leaf nodes in the hierarchy, the associated + * scheduler queue, %NULL on leaf nodes. + */ + struct bfq_sched_data *my_sched_data; + /* the scheduler queue this entity belongs to */ + struct bfq_sched_data *sched_data; + + /* flag, set to request a weight, ioprio or ioprio_class change */ + int prio_changed; +}; + +/** + * struct bfq_ttime - per process thinktime stats. + */ +struct bfq_ttime { + /* completion time of the last request */ + u64 last_end_request; + + /* total process thinktime */ + u64 ttime_total; + /* number of thinktime samples */ + unsigned long ttime_samples; + /* average process thinktime */ + u64 ttime_mean; +}; + +/** + * struct bfq_queue - leaf schedulable entity. + * + * A bfq_queue is a leaf request queue; it can be associated with an + * io_context or more, if it is async. + */ +struct bfq_queue { + /* reference counter */ + int ref; + /* parent bfq_data */ + struct bfq_data *bfqd; + + /* current ioprio and ioprio class */ + unsigned short ioprio, ioprio_class; + /* next ioprio and ioprio class if a change is in progress */ + unsigned short new_ioprio, new_ioprio_class; + + /* sorted list of pending requests */ + struct rb_root sort_list; + /* if fifo isn't expired, next request to serve */ + struct request *next_rq; + /* number of sync and async requests queued */ + int queued[2]; + /* number of requests currently allocated */ + int allocated; + /* number of pending metadata requests */ + int meta_pending; + /* fifo list of requests in sort_list */ + struct list_head fifo; + + /* entity representing this queue in the scheduler */ + struct bfq_entity entity; + + /* maximum budget allowed from the feedback mechanism */ + int max_budget; + /* budget expiration (in jiffies) */ + unsigned long budget_timeout; + + /* number of requests on the dispatch list or inside driver */ + int dispatched; + + /* status flags */ + unsigned long flags; + + /* node for active/idle bfqq list inside parent bfqd */ + struct list_head bfqq_list; + + /* associated @bfq_ttime struct */ + struct bfq_ttime ttime; + + /* bit vector: a 1 for each seeky requests in history */ + u32 seek_history; + /* position of the last request enqueued */ + sector_t last_request_pos; + + /* Number of consecutive pairs of request completion and + * arrival, such that the queue becomes idle after the + * completion, but the next request arrives within an idle + * time slice; used only if the queue's IO_bound flag has been + * cleared. + */ + unsigned int requests_within_timer; + + /* pid of the process owning the queue, used for logging purposes */ + pid_t pid; +}; + +/** + * struct bfq_io_cq - per (request_queue, io_context) structure. + */ +struct bfq_io_cq { + /* associated io_cq structure */ + struct io_cq icq; /* must be the first member */ + /* array of two process queues, the sync and the async */ + struct bfq_queue *bfqq[2]; + /* per (request_queue, blkcg) ioprio */ + int ioprio; +}; + +/** + * struct bfq_data - per-device data structure. + * + * All the fields are protected by @lock. + */ +struct bfq_data { + /* device request queue */ + struct request_queue *queue; + /* dispatch queue */ + struct list_head dispatch; + + /* root @bfq_sched_data for the device */ + struct bfq_sched_data sched_data; + + /* + * Number of bfq_queues containing requests (including the + * queue in service, even if it is idling). + */ + int busy_queues; + /* number of queued requests */ + int queued; + /* number of requests dispatched and waiting for completion */ + int rq_in_driver; + + /* + * Maximum number of requests in driver in the last + * @hw_tag_samples completed requests. + */ + int max_rq_in_driver; + /* number of samples used to calculate hw_tag */ + int hw_tag_samples; + /* flag set to one if the driver is showing a queueing behavior */ + int hw_tag; + + /* number of budgets assigned */ + int budgets_assigned; + + /* + * Timer set when idling (waiting) for the next request from + * the queue in service. + */ + struct hrtimer idle_slice_timer; + + /* bfq_queue in service */ + struct bfq_queue *in_service_queue; + /* bfq_io_cq (bic) associated with the @in_service_queue */ + struct bfq_io_cq *in_service_bic; + + /* on-disk position of the last served request */ + sector_t last_position; + + /* beginning of the last budget */ + ktime_t last_budget_start; + /* beginning of the last idle slice */ + ktime_t last_idling_start; + /* number of samples used to calculate @peak_rate */ + int peak_rate_samples; + /* + * Peak read/write rate, observed during the service of a + * budget [BFQ_RATE_SHIFT * sectors/usec]. The value is + * left-shifted by BFQ_RATE_SHIFT to increase precision in + * fixed-point calculations. + */ + u64 peak_rate; + /* maximum budget allotted to a bfq_queue before rescheduling */ + int bfq_max_budget; + + /* list of all the bfq_queues active on the device */ + struct list_head active_list; + /* list of all the bfq_queues idle on the device */ + struct list_head idle_list; + + /* + * Timeout for async/sync requests; when it fires, requests + * are served in fifo order. + */ + u64 bfq_fifo_expire[2]; + /* weight of backward seeks wrt forward ones */ + unsigned int bfq_back_penalty; + /* maximum allowed backward seek */ + unsigned int bfq_back_max; + /* maximum idling time */ + u32 bfq_slice_idle; + /* last time CLASS_IDLE was served */ + u64 bfq_class_idle_last_service; + + /* user-configured max budget value (0 for auto-tuning) */ + int bfq_user_max_budget; + /* + * Timeout for bfq_queues to consume their budget; used to + * prevent seeky queues from imposing long latencies to + * sequential or quasi-sequential ones (this also implies that + * seeky queues cannot receive guarantees in the service + * domain; after a timeout they are charged for the time they + * have been in service, to preserve fairness among them, but + * without service-domain guarantees). + */ + unsigned int bfq_timeout; + + /* + * Number of consecutive requests that must be issued within + * the idle time slice to set again idling to a queue which + * was marked as non-I/O-bound (see the definition of the + * IO_bound flag for further details). + */ + unsigned int bfq_requests_within_timer; + + /* + * Force device idling whenever needed to provide accurate + * service guarantees, without caring about throughput + * issues. CAVEAT: this may even increase latencies, in case + * of useless idling for processes that did stop doing I/O. + */ + bool strict_guarantees; + + /* fallback dummy bfqq for extreme OOM conditions */ + struct bfq_queue oom_bfqq; + + spinlock_t lock; + + /* + * bic associated with the task issuing current bio for + * merging. This and the next field are used as a support to + * be able to perform the bic lookup, needed by bio-merge + * functions, before the scheduler lock is taken, and thus + * avoid taking the request-queue lock while the scheduler + * lock is being held. + */ + struct bfq_io_cq *bio_bic; + /* bfqq associated with the task issuing current bio for merging */ + struct bfq_queue *bio_bfqq; +}; + +enum bfqq_state_flags { + BFQQF_busy = 0, /* has requests or is in service */ + BFQQF_wait_request, /* waiting for a request */ + BFQQF_non_blocking_wait_rq, /* + * waiting for a request + * without idling the device + */ + BFQQF_fifo_expire, /* FIFO checked in this slice */ + BFQQF_idle_window, /* slice idling enabled */ + BFQQF_sync, /* synchronous queue */ + BFQQF_budget_new, /* no completion with this budget */ + BFQQF_IO_bound, /* + * bfqq has timed-out at least once + * having consumed at most 2/10 of + * its budget + */ +}; + +#define BFQ_BFQQ_FNS(name) \ +static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \ +{ \ + __set_bit(BFQQF_##name, &(bfqq)->flags); \ +} \ +static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \ +{ \ + __clear_bit(BFQQF_##name, &(bfqq)->flags); \ +} \ +static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \ +{ \ + return test_bit(BFQQF_##name, &(bfqq)->flags); \ +} + +BFQ_BFQQ_FNS(busy); +BFQ_BFQQ_FNS(wait_request); +BFQ_BFQQ_FNS(non_blocking_wait_rq); +BFQ_BFQQ_FNS(fifo_expire); +BFQ_BFQQ_FNS(idle_window); +BFQ_BFQQ_FNS(sync); +BFQ_BFQQ_FNS(budget_new); +BFQ_BFQQ_FNS(IO_bound); +#undef BFQ_BFQQ_FNS + +/* Logging facilities. */ +#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \ + blk_add_trace_msg((bfqd)->queue, "bfq%d " fmt, (bfqq)->pid, ##args) + +#define bfq_log(bfqd, fmt, args...) \ + blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args) + +/* Expiration reasons. */ +enum bfqq_expiration { + BFQQE_TOO_IDLE = 0, /* + * queue has been idling for + * too long + */ + BFQQE_BUDGET_TIMEOUT, /* budget took too long to be used */ + BFQQE_BUDGET_EXHAUSTED, /* budget consumed */ + BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */ + BFQQE_PREEMPTED /* preemption in progress */ +}; + +static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity); + +static struct bfq_service_tree * +bfq_entity_service_tree(struct bfq_entity *entity) +{ + struct bfq_sched_data *sched_data = entity->sched_data; + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + unsigned int idx = bfqq ? bfqq->ioprio_class - 1 : + BFQ_DEFAULT_GRP_CLASS - 1; + + return sched_data->service_tree + idx; +} + +static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync) +{ + return bic->bfqq[is_sync]; +} + +static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, + bool is_sync) +{ + bic->bfqq[is_sync] = bfqq; +} + +static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic) +{ + return bic->icq.q->elevator->elevator_data; +} + +static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio); +static void bfq_put_queue(struct bfq_queue *bfqq); +static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, + struct bio *bio, bool is_sync, + struct bfq_io_cq *bic); +static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); + +/* + * Array of async queues for all the processes, one queue + * per ioprio value per ioprio_class. + */ +struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; +/* Async queue for the idle class (ioprio is ignored) */ +struct bfq_queue *async_idle_bfqq; + +/* Expiration time of sync (0) and async (1) requests, in ns. */ +static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 }; + +/* Maximum backwards seek (magic number lifted from CFQ), in KiB. */ +static const int bfq_back_max = 16 * 1024; + +/* Penalty of a backwards seek, in number of sectors. */ +static const int bfq_back_penalty = 2; + +/* Idling period duration, in ns. */ +static u64 bfq_slice_idle = NSEC_PER_SEC / 125; + +/* Minimum number of assigned budgets for which stats are safe to compute. */ +static const int bfq_stats_min_budgets = 194; + +/* Default maximum budget values, in sectors and number of requests. */ +static const int bfq_default_max_budget = 16 * 1024; + +/* Default timeout values, in jiffies, approximating CFQ defaults. */ +static const int bfq_timeout = HZ / 8; + +static struct kmem_cache *bfq_pool; + +/* Below this threshold (in ms), we consider thinktime immediate. */ +#define BFQ_MIN_TT (2 * NSEC_PER_MSEC) + +/* hw_tag detection: parallel requests threshold and min samples needed. */ +#define BFQ_HW_QUEUE_THRESHOLD 4 +#define BFQ_HW_QUEUE_SAMPLES 32 + +#define BFQQ_SEEK_THR (sector_t)(8 * 100) +#define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32) +#define BFQQ_CLOSE_THR (sector_t)(8 * 1024) +#define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8) + +/* Budget feedback step. */ +#define BFQ_BUDGET_STEP 128 + +/* Min samples used for peak rate estimation (for autotuning). */ +#define BFQ_PEAK_RATE_SAMPLES 32 + +/* Shift used for peak rate fixed precision calculations. */ +#define BFQ_RATE_SHIFT 16 + +#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \ + { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 }) + +#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0]) +#define RQ_BFQQ(rq) ((rq)->elv.priv[1]) + +/** + * icq_to_bic - convert iocontext queue structure to bfq_io_cq. + * @icq: the iocontext queue. + */ +static struct bfq_io_cq *icq_to_bic(struct io_cq *icq) +{ + /* bic->icq is the first member, %NULL will convert to %NULL */ + return container_of(icq, struct bfq_io_cq, icq); +} + +/** + * bfq_bic_lookup - search into @ioc a bic associated to @bfqd. + * @bfqd: the lookup key. + * @ioc: the io_context of the process doing I/O. + * @q: the request queue. + */ +static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd, + struct io_context *ioc, + struct request_queue *q) +{ + if (ioc) { + unsigned long flags; + struct bfq_io_cq *icq; + + spin_lock_irqsave(q->queue_lock, flags); + icq = icq_to_bic(ioc_lookup_icq(ioc, q)); + spin_unlock_irqrestore(q->queue_lock, flags); + + return icq; + } + + return NULL; +} + +/* + * Next two macros are just fake loops for the moment. They will + * become true loops in the cgroups-enabled variant of the code. Such + * a variant, in its turn, will be introduced by next commit. + */ +#define for_each_entity(entity) \ + for (; entity ; entity = NULL) + +#define for_each_entity_safe(entity, parent) \ + for (parent = NULL; entity ; entity = parent) + +static int bfq_update_next_in_service(struct bfq_sched_data *sd) +{ + return 0; +} + +static void bfq_check_next_in_service(struct bfq_sched_data *sd, + struct bfq_entity *entity) +{ +} + +static void bfq_update_budget(struct bfq_entity *next_in_service) +{ +} + +/* + * Shift for timestamp calculations. This actually limits the maximum + * service allowed in one timestamp delta (small shift values increase it), + * the maximum total weight that can be used for the queues in the system + * (big shift values increase it), and the period of virtual time + * wraparounds. + */ +#define WFQ_SERVICE_SHIFT 22 + +/** + * bfq_gt - compare two timestamps. + * @a: first ts. + * @b: second ts. + * + * Return @a > @b, dealing with wrapping correctly. + */ +static int bfq_gt(u64 a, u64 b) +{ + return (s64)(a - b) > 0; +} + +static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = NULL; + + if (!entity->my_sched_data) + bfqq = container_of(entity, struct bfq_queue, entity); + + return bfqq; +} + + +/** + * bfq_delta - map service into the virtual time domain. + * @service: amount of service. + * @weight: scale factor (weight of an entity or weight sum). + */ +static u64 bfq_delta(unsigned long service, unsigned long weight) +{ + u64 d = (u64)service << WFQ_SERVICE_SHIFT; + + do_div(d, weight); + return d; +} + +/** + * bfq_calc_finish - assign the finish time to an entity. + * @entity: the entity to act upon. + * @service: the service to be charged to the entity. + */ +static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + entity->finish = entity->start + + bfq_delta(service, entity->weight); + + if (bfqq) { + bfq_log_bfqq(bfqq->bfqd, bfqq, + "calc_finish: serv %lu, w %d", + service, entity->weight); + bfq_log_bfqq(bfqq->bfqd, bfqq, + "calc_finish: start %llu, finish %llu, delta %llu", + entity->start, entity->finish, + bfq_delta(service, entity->weight)); + } +} + +/** + * bfq_entity_of - get an entity from a node. + * @node: the node field of the entity. + * + * Convert a node pointer to the relative entity. This is used only + * to simplify the logic of some functions and not as the generic + * conversion mechanism because, e.g., in the tree walking functions, + * the check for a %NULL value would be redundant. + */ +static struct bfq_entity *bfq_entity_of(struct rb_node *node) +{ + struct bfq_entity *entity = NULL; + + if (node) + entity = rb_entry(node, struct bfq_entity, rb_node); + + return entity; +} + +/** + * bfq_extract - remove an entity from a tree. + * @root: the tree root. + * @entity: the entity to remove. + */ +static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) +{ + entity->tree = NULL; + rb_erase(&entity->rb_node, root); +} + +/** + * bfq_idle_extract - extract an entity from the idle tree. + * @st: the service tree of the owning @entity. + * @entity: the entity being removed. + */ +static void bfq_idle_extract(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *next; + + if (entity == st->first_idle) { + next = rb_next(&entity->rb_node); + st->first_idle = bfq_entity_of(next); + } + + if (entity == st->last_idle) { + next = rb_prev(&entity->rb_node); + st->last_idle = bfq_entity_of(next); + } + + bfq_extract(&st->idle, entity); + + if (bfqq) + list_del(&bfqq->bfqq_list); +} + +/** + * bfq_insert - generic tree insertion. + * @root: tree root. + * @entity: entity to insert. + * + * This is used for the idle and the active tree, since they are both + * ordered by finish time. + */ +static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) +{ + struct bfq_entity *entry; + struct rb_node **node = &root->rb_node; + struct rb_node *parent = NULL; + + while (*node) { + parent = *node; + entry = rb_entry(parent, struct bfq_entity, rb_node); + + if (bfq_gt(entry->finish, entity->finish)) + node = &parent->rb_left; + else + node = &parent->rb_right; + } + + rb_link_node(&entity->rb_node, parent, node); + rb_insert_color(&entity->rb_node, root); + + entity->tree = root; +} + +/** + * bfq_update_min - update the min_start field of a entity. + * @entity: the entity to update. + * @node: one of its children. + * + * This function is called when @entity may store an invalid value for + * min_start due to updates to the active tree. The function assumes + * that the subtree rooted at @node (which may be its left or its right + * child) has a valid min_start value. + */ +static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) +{ + struct bfq_entity *child; + + if (node) { + child = rb_entry(node, struct bfq_entity, rb_node); + if (bfq_gt(entity->min_start, child->min_start)) + entity->min_start = child->min_start; + } +} + +/** + * bfq_update_active_node - recalculate min_start. + * @node: the node to update. + * + * @node may have changed position or one of its children may have moved, + * this function updates its min_start value. The left and right subtrees + * are assumed to hold a correct min_start value. + */ +static void bfq_update_active_node(struct rb_node *node) +{ + struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); + + entity->min_start = entity->start; + bfq_update_min(entity, node->rb_right); + bfq_update_min(entity, node->rb_left); +} + +/** + * bfq_update_active_tree - update min_start for the whole active tree. + * @node: the starting node. + * + * @node must be the deepest modified node after an update. This function + * updates its min_start using the values held by its children, assuming + * that they did not change, and then updates all the nodes that may have + * changed in the path to the root. The only nodes that may have changed + * are the ones in the path or their siblings. + */ +static void bfq_update_active_tree(struct rb_node *node) +{ + struct rb_node *parent; + +up: + bfq_update_active_node(node); + + parent = rb_parent(node); + if (!parent) + return; + + if (node == parent->rb_left && parent->rb_right) + bfq_update_active_node(parent->rb_right); + else if (parent->rb_left) + bfq_update_active_node(parent->rb_left); + + node = parent; + goto up; +} + +/** + * bfq_active_insert - insert an entity in the active tree of its + * group/device. + * @st: the service tree of the entity. + * @entity: the entity being inserted. + * + * The active tree is ordered by finish time, but an extra key is kept + * per each node, containing the minimum value for the start times of + * its children (and the node itself), so it's possible to search for + * the eligible node with the lowest finish time in logarithmic time. + */ +static void bfq_active_insert(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *node = &entity->rb_node; + + bfq_insert(&st->active, entity); + + if (node->rb_left) + node = node->rb_left; + else if (node->rb_right) + node = node->rb_right; + + bfq_update_active_tree(node); + + if (bfqq) + list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); +} + +/** + * bfq_ioprio_to_weight - calc a weight from an ioprio. + * @ioprio: the ioprio value to convert. + */ +static unsigned short bfq_ioprio_to_weight(int ioprio) +{ + return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; +} + +/** + * bfq_weight_to_ioprio - calc an ioprio from a weight. + * @weight: the weight value to convert. + * + * To preserve as much as possible the old only-ioprio user interface, + * 0 is used as an escape ioprio value for weights (numerically) equal or + * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF. + */ +static unsigned short bfq_weight_to_ioprio(int weight) +{ + return max_t(int, 0, + IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight); +} + +static void bfq_get_entity(struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + if (bfqq) { + bfqq->ref++; + bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", + bfqq, bfqq->ref); + } +} + +/** + * bfq_find_deepest - find the deepest node that an extraction can modify. + * @node: the node being removed. + * + * Do the first step of an extraction in an rb tree, looking for the + * node that will replace @node, and returning the deepest node that + * the following modifications to the tree can touch. If @node is the + * last node in the tree return %NULL. + */ +static struct rb_node *bfq_find_deepest(struct rb_node *node) +{ + struct rb_node *deepest; + + if (!node->rb_right && !node->rb_left) + deepest = rb_parent(node); + else if (!node->rb_right) + deepest = node->rb_left; + else if (!node->rb_left) + deepest = node->rb_right; + else { + deepest = rb_next(node); + if (deepest->rb_right) + deepest = deepest->rb_right; + else if (rb_parent(deepest) != node) + deepest = rb_parent(deepest); + } + + return deepest; +} + +/** + * bfq_active_extract - remove an entity from the active tree. + * @st: the service_tree containing the tree. + * @entity: the entity being removed. + */ +static void bfq_active_extract(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *node; + + node = bfq_find_deepest(&entity->rb_node); + bfq_extract(&st->active, entity); + + if (node) + bfq_update_active_tree(node); + + if (bfqq) + list_del(&bfqq->bfqq_list); +} + +/** + * bfq_idle_insert - insert an entity into the idle tree. + * @st: the service tree containing the tree. + * @entity: the entity to insert. + */ +static void bfq_idle_insert(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct bfq_entity *first_idle = st->first_idle; + struct bfq_entity *last_idle = st->last_idle; + + if (!first_idle || bfq_gt(first_idle->finish, entity->finish)) + st->first_idle = entity; + if (!last_idle || bfq_gt(entity->finish, last_idle->finish)) + st->last_idle = entity; + + bfq_insert(&st->idle, entity); + + if (bfqq) + list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); +} + +/** + * bfq_forget_entity - do not consider entity any longer for scheduling + * @st: the service tree. + * @entity: the entity being removed. + * @is_in_service: true if entity is currently the in-service entity. + * + * Forget everything about @entity. In addition, if entity represents + * a queue, and the latter is not in service, then release the service + * reference to the queue (the one taken through bfq_get_entity). In + * fact, in this case, there is really no more service reference to + * the queue, as the latter is also outside any service tree. If, + * instead, the queue is in service, then __bfq_bfqd_reset_in_service + * will take care of putting the reference when the queue finally + * stops being served. + */ +static void bfq_forget_entity(struct bfq_service_tree *st, + struct bfq_entity *entity, + bool is_in_service) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + entity->on_st = 0; + st->wsum -= entity->weight; + if (bfqq && !is_in_service) + bfq_put_queue(bfqq); +} + +/** + * bfq_put_idle_entity - release the idle tree ref of an entity. + * @st: service tree for the entity. + * @entity: the entity being released. + */ +static void bfq_put_idle_entity(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + bfq_idle_extract(st, entity); + bfq_forget_entity(st, entity, + entity == entity->sched_data->in_service_entity); +} + +/** + * bfq_forget_idle - update the idle tree if necessary. + * @st: the service tree to act upon. + * + * To preserve the global O(log N) complexity we only remove one entry here; + * as the idle tree will not grow indefinitely this can be done safely. + */ +static void bfq_forget_idle(struct bfq_service_tree *st) +{ + struct bfq_entity *first_idle = st->first_idle; + struct bfq_entity *last_idle = st->last_idle; + + if (RB_EMPTY_ROOT(&st->active) && last_idle && + !bfq_gt(last_idle->finish, st->vtime)) { + /* + * Forget the whole idle tree, increasing the vtime past + * the last finish time of idle entities. + */ + st->vtime = last_idle->finish; + } + + if (first_idle && !bfq_gt(first_idle->finish, st->vtime)) + bfq_put_idle_entity(st, first_idle); +} + +static struct bfq_service_tree * +__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, + struct bfq_entity *entity) +{ + struct bfq_service_tree *new_st = old_st; + + if (entity->prio_changed) { + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + unsigned short prev_weight, new_weight; + struct bfq_data *bfqd = NULL; + + if (bfqq) + bfqd = bfqq->bfqd; + + old_st->wsum -= entity->weight; + + if (entity->new_weight != entity->orig_weight) { + if (entity->new_weight < BFQ_MIN_WEIGHT || + entity->new_weight > BFQ_MAX_WEIGHT) { + pr_crit("update_weight_prio: new_weight %d\n", + entity->new_weight); + if (entity->new_weight < BFQ_MIN_WEIGHT) + entity->new_weight = BFQ_MIN_WEIGHT; + else + entity->new_weight = BFQ_MAX_WEIGHT; + } + entity->orig_weight = entity->new_weight; + if (bfqq) + bfqq->ioprio = + bfq_weight_to_ioprio(entity->orig_weight); + } + + if (bfqq) + bfqq->ioprio_class = bfqq->new_ioprio_class; + entity->prio_changed = 0; + + /* + * NOTE: here we may be changing the weight too early, + * this will cause unfairness. The correct approach + * would have required additional complexity to defer + * weight changes to the proper time instants (i.e., + * when entity->finish <= old_st->vtime). + */ + new_st = bfq_entity_service_tree(entity); + + prev_weight = entity->weight; + new_weight = entity->orig_weight; + entity->weight = new_weight; + + new_st->wsum += entity->weight; + + if (new_st != old_st) + entity->start = new_st->vtime; + } + + return new_st; +} + +/** + * bfq_bfqq_served - update the scheduler status after selection for + * service. + * @bfqq: the queue being served. + * @served: bytes to transfer. + * + * NOTE: this can be optimized, as the timestamps of upper level entities + * are synchronized every time a new bfqq is selected for service. By now, + * we keep it to better check consistency. + */ +static void bfq_bfqq_served(struct bfq_queue *bfqq, int served) +{ + struct bfq_entity *entity = &bfqq->entity; + struct bfq_service_tree *st; + + for_each_entity(entity) { + st = bfq_entity_service_tree(entity); + + entity->service += served; + + st->vtime += bfq_delta(served, st->wsum); + bfq_forget_idle(st); + } + bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served); +} + +/** + * bfq_bfqq_charge_full_budget - set the service to the entity budget. + * @bfqq: the queue that needs a service update. + * + * When it's not possible to be fair in the service domain, because + * a queue is not consuming its budget fast enough (the meaning of + * fast depends on the timeout parameter), we charge it a full + * budget. In this way we should obtain a sort of time-domain + * fairness among all the seeky/slow queues. + */ +static void bfq_bfqq_charge_full_budget(struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + + bfq_log_bfqq(bfqq->bfqd, bfqq, "charge_full_budget"); + + bfq_bfqq_served(bfqq, entity->budget - entity->service); +} + +/** + * __bfq_activate_entity - activate an entity. + * @entity: the entity being activated. + * @non_blocking_wait_rq: true if this entity was waiting for a request + * + * Called whenever an entity is activated, i.e., it is not active and one + * of its children receives a new request, or has to be reactivated due to + * budget exhaustion. It uses the current budget of the entity (and the + * service received if @entity is active) of the queue to calculate its + * timestamps. + */ +static void __bfq_activate_entity(struct bfq_entity *entity, + bool non_blocking_wait_rq) +{ + struct bfq_sched_data *sd = entity->sched_data; + struct bfq_service_tree *st = bfq_entity_service_tree(entity); + bool backshifted = false; + + if (entity == sd->in_service_entity) { + /* + * If we are requeueing the current entity we have + * to take care of not charging to it service it has + * not received. + */ + bfq_calc_finish(entity, entity->service); + entity->start = entity->finish; + sd->in_service_entity = NULL; + } else if (entity->tree == &st->active) { + /* + * Requeueing an entity due to a change of some + * next_in_service entity below it. We reuse the + * old start time. + */ + bfq_active_extract(st, entity); + } else { + unsigned long long min_vstart; + + /* See comments on bfq_fqq_update_budg_for_activation */ + if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) { + backshifted = true; + min_vstart = entity->finish; + } else + min_vstart = st->vtime; + + if (entity->tree == &st->idle) { + /* + * Must be on the idle tree, bfq_idle_extract() will + * check for that. + */ + bfq_idle_extract(st, entity); + entity->start = bfq_gt(min_vstart, entity->finish) ? + min_vstart : entity->finish; + } else { + /* + * The finish time of the entity may be invalid, and + * it is in the past for sure, otherwise the queue + * would have been on the idle tree. + */ + entity->start = min_vstart; + st->wsum += entity->weight; + /* + * entity is about to be inserted into a service tree, + * and then set in service: get a reference to make + * sure entity does not disappear until it is no + * longer in service or scheduled for service. + */ + bfq_get_entity(entity); + + entity->on_st = 1; + } + } + + st = __bfq_entity_update_weight_prio(st, entity); + bfq_calc_finish(entity, entity->budget); + + /* + * If some queues enjoy backshifting for a while, then their + * (virtual) finish timestamps may happen to become lower and + * lower than the system virtual time. In particular, if + * these queues often happen to be idle for short time + * periods, and during such time periods other queues with + * higher timestamps happen to be busy, then the backshifted + * timestamps of the former queues can become much lower than + * the system virtual time. In fact, to serve the queues with + * higher timestamps while the ones with lower timestamps are + * idle, the system virtual time may be pushed-up to much + * higher values than the finish timestamps of the idle + * queues. As a consequence, the finish timestamps of all new + * or newly activated queues may end up being much larger than + * those of lucky queues with backshifted timestamps. The + * latter queues may then monopolize the device for a lot of + * time. This would simply break service guarantees. + * + * To reduce this problem, push up a little bit the + * backshifted timestamps of the queue associated with this + * entity (only a queue can happen to have the backshifted + * flag set): just enough to let the finish timestamp of the + * queue be equal to the current value of the system virtual + * time. This may introduce a little unfairness among queues + * with backshifted timestamps, but it does not break + * worst-case fairness guarantees. + */ + if (backshifted && bfq_gt(st->vtime, entity->finish)) { + unsigned long delta = st->vtime - entity->finish; + + entity->start += delta; + entity->finish += delta; + } + + bfq_active_insert(st, entity); +} + +/** + * bfq_activate_entity - activate an entity and its ancestors if necessary. + * @entity: the entity to activate. + * @non_blocking_wait_rq: true if this entity was waiting for a request + * + * Activate @entity and all the entities on the path from it to the root. + */ +static void bfq_activate_entity(struct bfq_entity *entity, + bool non_blocking_wait_rq) +{ + struct bfq_sched_data *sd; + + for_each_entity(entity) { + __bfq_activate_entity(entity, non_blocking_wait_rq); + + sd = entity->sched_data; + if (!bfq_update_next_in_service(sd)) + /* + * No need to propagate the activation to the + * upper entities, as they will be updated when + * the in-service entity is rescheduled. + */ + break; + } +} + +/** + * __bfq_deactivate_entity - deactivate an entity from its service tree. + * @entity: the entity to deactivate. + * @requeue: if false, the entity will not be put into the idle tree. + * + * Deactivate an entity, independently from its previous state. If the + * entity was not on a service tree just return, otherwise if it is on + * any scheduler tree, extract it from that tree, and if necessary + * and if the caller did not specify @requeue, put it on the idle tree. + * + * Return %1 if the caller should update the entity hierarchy, i.e., + * if the entity was in service or if it was the next_in_service for + * its sched_data; return %0 otherwise. + */ +static int __bfq_deactivate_entity(struct bfq_entity *entity, int requeue) +{ + struct bfq_sched_data *sd = entity->sched_data; + struct bfq_service_tree *st = bfq_entity_service_tree(entity); + int is_in_service = entity == sd->in_service_entity; + int ret = 0; + + if (!entity->on_st) + return 0; + + if (is_in_service) { + bfq_calc_finish(entity, entity->service); + sd->in_service_entity = NULL; + } else if (entity->tree == &st->active) + bfq_active_extract(st, entity); + else if (entity->tree == &st->idle) + bfq_idle_extract(st, entity); + + if (is_in_service || sd->next_in_service == entity) + ret = bfq_update_next_in_service(sd); + + if (!requeue || !bfq_gt(entity->finish, st->vtime)) + bfq_forget_entity(st, entity, is_in_service); + else + bfq_idle_insert(st, entity); + + return ret; +} + +/** + * bfq_deactivate_entity - deactivate an entity. + * @entity: the entity to deactivate. + * @requeue: true if the entity can be put on the idle tree + */ +static void bfq_deactivate_entity(struct bfq_entity *entity, int requeue) +{ + struct bfq_sched_data *sd; + struct bfq_entity *parent = NULL; + + for_each_entity_safe(entity, parent) { + sd = entity->sched_data; + + if (!__bfq_deactivate_entity(entity, requeue)) + /* + * The parent entity is still backlogged, and + * we don't need to update it as it is still + * in service. + */ + break; + + if (sd->next_in_service) + /* + * The parent entity is still backlogged and + * the budgets on the path towards the root + * need to be updated. + */ + goto update; + + /* + * If we get here, then the parent is no more backlogged and + * we want to propagate the deactivation upwards. + */ + requeue = 1; + } + + return; + +update: + entity = parent; + for_each_entity(entity) { + __bfq_activate_entity(entity, false); + + sd = entity->sched_data; + if (!bfq_update_next_in_service(sd)) + break; + } +} + +/** + * bfq_update_vtime - update vtime if necessary. + * @st: the service tree to act upon. + * + * If necessary update the service tree vtime to have at least one + * eligible entity, skipping to its start time. Assumes that the + * active tree of the device is not empty. + * + * NOTE: this hierarchical implementation updates vtimes quite often, + * we may end up with reactivated processes getting timestamps after a + * vtime skip done because we needed a ->first_active entity on some + * intermediate node. + */ +static void bfq_update_vtime(struct bfq_service_tree *st) +{ + struct bfq_entity *entry; + struct rb_node *node = st->active.rb_node; + + entry = rb_entry(node, struct bfq_entity, rb_node); + if (bfq_gt(entry->min_start, st->vtime)) { + st->vtime = entry->min_start; + bfq_forget_idle(st); + } +} + +/** + * bfq_first_active_entity - find the eligible entity with + * the smallest finish time + * @st: the service tree to select from. + * + * This function searches the first schedulable entity, starting from the + * root of the tree and going on the left every time on this side there is + * a subtree with at least one eligible (start >= vtime) entity. The path on + * the right is followed only if a) the left subtree contains no eligible + * entities and b) no eligible entity has been found yet. + */ +static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st) +{ + struct bfq_entity *entry, *first = NULL; + struct rb_node *node = st->active.rb_node; + + while (node) { + entry = rb_entry(node, struct bfq_entity, rb_node); +left: + if (!bfq_gt(entry->start, st->vtime)) + first = entry; + + if (node->rb_left) { + entry = rb_entry(node->rb_left, + struct bfq_entity, rb_node); + if (!bfq_gt(entry->min_start, st->vtime)) { + node = node->rb_left; + goto left; + } + } + if (first) + break; + node = node->rb_right; + } + + return first; +} + +/** + * __bfq_lookup_next_entity - return the first eligible entity in @st. + * @st: the service tree. + * + * Update the virtual time in @st and return the first eligible entity + * it contains. + */ +static struct bfq_entity *__bfq_lookup_next_entity(struct bfq_service_tree *st, + bool force) +{ + struct bfq_entity *entity, *new_next_in_service = NULL; + + if (RB_EMPTY_ROOT(&st->active)) + return NULL; + + bfq_update_vtime(st); + entity = bfq_first_active_entity(st); + + /* + * If the chosen entity does not match with the sched_data's + * next_in_service and we are forcedly serving the IDLE priority + * class tree, bubble up budget update. + */ + if (unlikely(force && entity != entity->sched_data->next_in_service)) { + new_next_in_service = entity; + for_each_entity(new_next_in_service) + bfq_update_budget(new_next_in_service); + } + + return entity; +} + +/** + * bfq_lookup_next_entity - return the first eligible entity in @sd. + * @sd: the sched_data. + * @extract: if true the returned entity will be also extracted from @sd. + * + * NOTE: since we cache the next_in_service entity at each level of the + * hierarchy, the complexity of the lookup can be decreased with + * absolutely no effort just returning the cached next_in_service value; + * we prefer to do full lookups to test the consistency of the data + * structures. + */ +static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, + int extract, + struct bfq_data *bfqd) +{ + struct bfq_service_tree *st = sd->service_tree; + struct bfq_entity *entity; + int i = 0; + + /* + * Choose from idle class, if needed to guarantee a minimum + * bandwidth to this class. This should also mitigate + * priority-inversion problems in case a low priority task is + * holding file system resources. + */ + if (bfqd && + jiffies - bfqd->bfq_class_idle_last_service > + BFQ_CL_IDLE_TIMEOUT) { + entity = __bfq_lookup_next_entity(st + BFQ_IOPRIO_CLASSES - 1, + true); + if (entity) { + i = BFQ_IOPRIO_CLASSES - 1; + bfqd->bfq_class_idle_last_service = jiffies; + sd->next_in_service = entity; + } + } + for (; i < BFQ_IOPRIO_CLASSES; i++) { + entity = __bfq_lookup_next_entity(st + i, false); + if (entity) { + if (extract) { + bfq_check_next_in_service(sd, entity); + bfq_active_extract(st + i, entity); + sd->in_service_entity = entity; + sd->next_in_service = NULL; + } + break; + } + } + + return entity; +} + +static bool next_queue_may_preempt(struct bfq_data *bfqd) +{ + struct bfq_sched_data *sd = &bfqd->sched_data; + + return sd->next_in_service != sd->in_service_entity; +} + + +/* + * Get next queue for service. + */ +static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) +{ + struct bfq_entity *entity = NULL; + struct bfq_sched_data *sd; + struct bfq_queue *bfqq; + + if (bfqd->busy_queues == 0) + return NULL; + + sd = &bfqd->sched_data; + for (; sd ; sd = entity->my_sched_data) { + entity = bfq_lookup_next_entity(sd, 1, bfqd); + entity->service = 0; + } + + bfqq = bfq_entity_to_bfqq(entity); + + return bfqq; +} + +static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) +{ + struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; + struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; + + if (bfqd->in_service_bic) { + put_io_context(bfqd->in_service_bic->icq.ioc); + bfqd->in_service_bic = NULL; + } + + bfq_clear_bfqq_wait_request(in_serv_bfqq); + hrtimer_try_to_cancel(&bfqd->idle_slice_timer); + bfqd->in_service_queue = NULL; + + /* + * in_serv_entity is no longer in service, so, if it is in no + * service tree either, then release the service reference to + * the queue it represents (taken with bfq_get_entity). + */ + if (!in_serv_entity->on_st) + bfq_put_queue(in_serv_bfqq); +} + +static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, + int requeue) +{ + struct bfq_entity *entity = &bfqq->entity; + + bfq_deactivate_entity(entity, requeue); +} + +static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + + bfq_activate_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq)); + bfq_clear_bfqq_non_blocking_wait_rq(bfqq); +} + +/* + * Called when the bfqq no longer has requests pending, remove it from + * the service tree. + */ +static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, + int requeue) +{ + bfq_log_bfqq(bfqd, bfqq, "del from busy"); + + bfq_clear_bfqq_busy(bfqq); + + bfqd->busy_queues--; + + bfq_deactivate_bfqq(bfqd, bfqq, requeue); +} + +/* + * Called when an inactive queue receives a new request. + */ +static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + bfq_log_bfqq(bfqd, bfqq, "add to busy"); + + bfq_activate_bfqq(bfqd, bfqq); + + bfq_mark_bfqq_busy(bfqq); + bfqd->busy_queues++; +} + +static void bfq_init_entity(struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + entity->weight = entity->new_weight; + entity->orig_weight = entity->new_weight; + + bfqq->ioprio = bfqq->new_ioprio; + bfqq->ioprio_class = bfqq->new_ioprio_class; + + entity->sched_data = &bfqq->bfqd->sched_data; +} + +#define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE) +#define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT) + +#define bfq_sample_valid(samples) ((samples) > 80) + +/* + * Scheduler run of queue, if there are requests pending and no one in the + * driver that will restart queueing. + */ +static void bfq_schedule_dispatch(struct bfq_data *bfqd) +{ + if (bfqd->queued != 0) { + bfq_log(bfqd, "schedule dispatch"); + blk_mq_run_hw_queues(bfqd->queue, true); + } +} + +/* + * Lifted from AS - choose which of rq1 and rq2 that is best served now. + * We choose the request that is closesr to the head right now. Distance + * behind the head is penalized and only allowed to a certain extent. + */ +static struct request *bfq_choose_req(struct bfq_data *bfqd, + struct request *rq1, + struct request *rq2, + sector_t last) +{ + sector_t s1, s2, d1 = 0, d2 = 0; + unsigned long back_max; +#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */ +#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */ + unsigned int wrap = 0; /* bit mask: requests behind the disk head? */ + + if (!rq1 || rq1 == rq2) + return rq2; + if (!rq2) + return rq1; + + if (rq_is_sync(rq1) && !rq_is_sync(rq2)) + return rq1; + else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) + return rq2; + if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) + return rq1; + else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META)) + return rq2; + + s1 = blk_rq_pos(rq1); + s2 = blk_rq_pos(rq2); + + /* + * By definition, 1KiB is 2 sectors. + */ + back_max = bfqd->bfq_back_max * 2; + + /* + * Strict one way elevator _except_ in the case where we allow + * short backward seeks which are biased as twice the cost of a + * similar forward seek. + */ + if (s1 >= last) + d1 = s1 - last; + else if (s1 + back_max >= last) + d1 = (last - s1) * bfqd->bfq_back_penalty; + else + wrap |= BFQ_RQ1_WRAP; + + if (s2 >= last) + d2 = s2 - last; + else if (s2 + back_max >= last) + d2 = (last - s2) * bfqd->bfq_back_penalty; + else + wrap |= BFQ_RQ2_WRAP; + + /* Found required data */ + + /* + * By doing switch() on the bit mask "wrap" we avoid having to + * check two variables for all permutations: --> faster! + */ + switch (wrap) { + case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ + if (d1 < d2) + return rq1; + else if (d2 < d1) + return rq2; + + if (s1 >= s2) + return rq1; + else + return rq2; + + case BFQ_RQ2_WRAP: + return rq1; + case BFQ_RQ1_WRAP: + return rq2; + case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */ + default: + /* + * Since both rqs are wrapped, + * start with the one that's further behind head + * (--> only *one* back seek required), + * since back seek takes more time than forward. + */ + if (s1 <= s2) + return rq1; + else + return rq2; + } +} + +/* + * Return expired entry, or NULL to just start from scratch in rbtree. + */ +static struct request *bfq_check_fifo(struct bfq_queue *bfqq, + struct request *last) +{ + struct request *rq; + + if (bfq_bfqq_fifo_expire(bfqq)) + return NULL; + + bfq_mark_bfqq_fifo_expire(bfqq); + + rq = rq_entry_fifo(bfqq->fifo.next); + + if (rq == last || ktime_get_ns() < rq->fifo_time) + return NULL; + + bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq); + return rq; +} + +static struct request *bfq_find_next_rq(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct request *last) +{ + struct rb_node *rbnext = rb_next(&last->rb_node); + struct rb_node *rbprev = rb_prev(&last->rb_node); + struct request *next, *prev = NULL; + + /* Follow expired path, else get first next available. */ + next = bfq_check_fifo(bfqq, last); + if (next) + return next; + + if (rbprev) + prev = rb_entry_rq(rbprev); + + if (rbnext) + next = rb_entry_rq(rbnext); + else { + rbnext = rb_first(&bfqq->sort_list); + if (rbnext && rbnext != &last->rb_node) + next = rb_entry_rq(rbnext); + } + + return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last)); +} + +static unsigned long bfq_serv_to_charge(struct request *rq, + struct bfq_queue *bfqq) +{ + return blk_rq_sectors(rq); +} + +/** + * bfq_updated_next_req - update the queue after a new next_rq selection. + * @bfqd: the device data the queue belongs to. + * @bfqq: the queue to update. + * + * If the first request of a queue changes we make sure that the queue + * has enough budget to serve at least its first request (if the + * request has grown). We do this because if the queue has not enough + * budget for its first request, it has to go through two dispatch + * rounds to actually get it dispatched. + */ +static void bfq_updated_next_req(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + struct request *next_rq = bfqq->next_rq; + unsigned long new_budget; + + if (!next_rq) + return; + + if (bfqq == bfqd->in_service_queue) + /* + * In order not to break guarantees, budgets cannot be + * changed after an entity has been selected. + */ + return; + + new_budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(next_rq, bfqq)); + if (entity->budget != new_budget) { + entity->budget = new_budget; + bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", + new_budget); + bfq_activate_bfqq(bfqd, bfqq); + } +} + +static int bfq_bfqq_budget_left(struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + + return entity->budget - entity->service; +} + +/* + * If enough samples have been computed, return the current max budget + * stored in bfqd, which is dynamically updated according to the + * estimated disk peak rate; otherwise return the default max budget + */ +static int bfq_max_budget(struct bfq_data *bfqd) +{ + if (bfqd->budgets_assigned < bfq_stats_min_budgets) + return bfq_default_max_budget; + else + return bfqd->bfq_max_budget; +} + +/* + * Return min budget, which is a fraction of the current or default + * max budget (trying with 1/32) + */ +static int bfq_min_budget(struct bfq_data *bfqd) +{ + if (bfqd->budgets_assigned < bfq_stats_min_budgets) + return bfq_default_max_budget / 32; + else + return bfqd->bfq_max_budget / 32; +} + +static void bfq_bfqq_expire(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + bool compensate, + enum bfqq_expiration reason); + +/* + * The next function, invoked after the input queue bfqq switches from + * idle to busy, updates the budget of bfqq. The function also tells + * whether the in-service queue should be expired, by returning + * true. The purpose of expiring the in-service queue is to give bfqq + * the chance to possibly preempt the in-service queue, and the reason + * for preempting the in-service queue is to achieve the following + * goal: guarantee to bfqq its reserved bandwidth even if bfqq has + * expired because it has remained idle. + * + * In particular, bfqq may have expired for one of the following two + * reasons: + * + * - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling + * and did not make it to issue a new request before its last + * request was served; + * + * - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue + * a new request before the expiration of the idling-time. + * + * Even if bfqq has expired for one of the above reasons, the process + * associated with the queue may be however issuing requests greedily, + * and thus be sensitive to the bandwidth it receives (bfqq may have + * remained idle for other reasons: CPU high load, bfqq not enjoying + * idling, I/O throttling somewhere in the path from the process to + * the I/O scheduler, ...). But if, after every expiration for one of + * the above two reasons, bfqq has to wait for the service of at least + * one full budget of another queue before being served again, then + * bfqq is likely to get a much lower bandwidth or resource time than + * its reserved ones. To address this issue, two countermeasures need + * to be taken. + * + * First, the budget and the timestamps of bfqq need to be updated in + * a special way on bfqq reactivation: they need to be updated as if + * bfqq did not remain idle and did not expire. In fact, if they are + * computed as if bfqq expired and remained idle until reactivation, + * then the process associated with bfqq is treated as if, instead of + * being greedy, it stopped issuing requests when bfqq remained idle, + * and restarts issuing requests only on this reactivation. In other + * words, the scheduler does not help the process recover the "service + * hole" between bfqq expiration and reactivation. As a consequence, + * the process receives a lower bandwidth than its reserved one. In + * contrast, to recover this hole, the budget must be updated as if + * bfqq was not expired at all before this reactivation, i.e., it must + * be set to the value of the remaining budget when bfqq was + * expired. Along the same line, timestamps need to be assigned the + * value they had the last time bfqq was selected for service, i.e., + * before last expiration. Thus timestamps need to be back-shifted + * with respect to their normal computation (see [1] for more details + * on this tricky aspect). + * + * Secondly, to allow the process to recover the hole, the in-service + * queue must be expired too, to give bfqq the chance to preempt it + * immediately. In fact, if bfqq has to wait for a full budget of the + * in-service queue to be completed, then it may become impossible to + * let the process recover the hole, even if the back-shifted + * timestamps of bfqq are lower than those of the in-service queue. If + * this happens for most or all of the holes, then the process may not + * receive its reserved bandwidth. In this respect, it is worth noting + * that, being the service of outstanding requests unpreemptible, a + * little fraction of the holes may however be unrecoverable, thereby + * causing a little loss of bandwidth. + * + * The last important point is detecting whether bfqq does need this + * bandwidth recovery. In this respect, the next function deems the + * process associated with bfqq greedy, and thus allows it to recover + * the hole, if: 1) the process is waiting for the arrival of a new + * request (which implies that bfqq expired for one of the above two + * reasons), and 2) such a request has arrived soon. The first + * condition is controlled through the flag non_blocking_wait_rq, + * while the second through the flag arrived_in_time. If both + * conditions hold, then the function computes the budget in the + * above-described special way, and signals that the in-service queue + * should be expired. Timestamp back-shifting is done later in + * __bfq_activate_entity. + */ +static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + bool arrived_in_time) +{ + struct bfq_entity *entity = &bfqq->entity; + + if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) { + /* + * We do not clear the flag non_blocking_wait_rq here, as + * the latter is used in bfq_activate_bfqq to signal + * that timestamps need to be back-shifted (and is + * cleared right after). + */ + + /* + * In next assignment we rely on that either + * entity->service or entity->budget are not updated + * on expiration if bfqq is empty (see + * __bfq_bfqq_recalc_budget). Thus both quantities + * remain unchanged after such an expiration, and the + * following statement therefore assigns to + * entity->budget the remaining budget on such an + * expiration. For clarity, entity->service is not + * updated on expiration in any case, and, in normal + * operation, is reset only when bfqq is selected for + * service (see bfq_get_next_queue). + */ + entity->budget = min_t(unsigned long, + bfq_bfqq_budget_left(bfqq), + bfqq->max_budget); + + return true; + } + + entity->budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(bfqq->next_rq, bfqq)); + bfq_clear_bfqq_non_blocking_wait_rq(bfqq); + return false; +} + +static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct request *rq) +{ + bool bfqq_wants_to_preempt, + /* + * See the comments on + * bfq_bfqq_update_budg_for_activation for + * details on the usage of the next variable. + */ + arrived_in_time = ktime_get_ns() <= + bfqq->ttime.last_end_request + + bfqd->bfq_slice_idle * 3; + + /* + * Update budget and check whether bfqq may want to preempt + * the in-service queue. + */ + bfqq_wants_to_preempt = + bfq_bfqq_update_budg_for_activation(bfqd, bfqq, + arrived_in_time); + + if (!bfq_bfqq_IO_bound(bfqq)) { + if (arrived_in_time) { + bfqq->requests_within_timer++; + if (bfqq->requests_within_timer >= + bfqd->bfq_requests_within_timer) + bfq_mark_bfqq_IO_bound(bfqq); + } else + bfqq->requests_within_timer = 0; + } + + bfq_add_bfqq_busy(bfqd, bfqq); + + /* + * Expire in-service queue only if preemption may be needed + * for guarantees. In this respect, the function + * next_queue_may_preempt just checks a simple, necessary + * condition, and not a sufficient condition based on + * timestamps. In fact, for the latter condition to be + * evaluated, timestamps would need first to be updated, and + * this operation is quite costly (see the comments on the + * function bfq_bfqq_update_budg_for_activation). + */ + if (bfqd->in_service_queue && bfqq_wants_to_preempt && + next_queue_may_preempt(bfqd)) + bfq_bfqq_expire(bfqd, bfqd->in_service_queue, + false, BFQQE_PREEMPTED); +} + +static void bfq_add_request(struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_data *bfqd = bfqq->bfqd; + struct request *next_rq, *prev; + + bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); + bfqq->queued[rq_is_sync(rq)]++; + bfqd->queued++; + + elv_rb_add(&bfqq->sort_list, rq); + + /* + * Check if this request is a better next-serve candidate. + */ + prev = bfqq->next_rq; + next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position); + bfqq->next_rq = next_rq; + + if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */ + bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, rq); + else if (prev != bfqq->next_rq) + bfq_updated_next_req(bfqd, bfqq); +} + +static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd, + struct bio *bio, + struct request_queue *q) +{ + struct bfq_queue *bfqq = bfqd->bio_bfqq; + + + if (bfqq) + return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio)); + + return NULL; +} + +#if 0 /* Still not clear if we can do without next two functions */ +static void bfq_activate_request(struct request_queue *q, struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + + bfqd->rq_in_driver++; + bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); + bfq_log(bfqd, "activate_request: new bfqd->last_position %llu", + (unsigned long long)bfqd->last_position); +} + +static void bfq_deactivate_request(struct request_queue *q, struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + + bfqd->rq_in_driver--; +} +#endif + +static void bfq_remove_request(struct request_queue *q, + struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_data *bfqd = bfqq->bfqd; + const int sync = rq_is_sync(rq); + + if (bfqq->next_rq == rq) { + bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq); + bfq_updated_next_req(bfqd, bfqq); + } + + if (rq->queuelist.prev != &rq->queuelist) + list_del_init(&rq->queuelist); + bfqq->queued[sync]--; + bfqd->queued--; + elv_rb_del(&bfqq->sort_list, rq); + + elv_rqhash_del(q, rq); + if (q->last_merge == rq) + q->last_merge = NULL; + + if (RB_EMPTY_ROOT(&bfqq->sort_list)) { + bfqq->next_rq = NULL; + + if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) { + bfq_del_bfqq_busy(bfqd, bfqq, 1); + /* + * bfqq emptied. In normal operation, when + * bfqq is empty, bfqq->entity.service and + * bfqq->entity.budget must contain, + * respectively, the service received and the + * budget used last time bfqq emptied. These + * facts do not hold in this case, as at least + * this last removal occurred while bfqq is + * not in service. To avoid inconsistencies, + * reset both bfqq->entity.service and + * bfqq->entity.budget, if bfqq has still a + * process that may issue I/O requests to it. + */ + bfqq->entity.budget = bfqq->entity.service = 0; + } + } + + if (rq->cmd_flags & REQ_META) + bfqq->meta_pending--; +} + +static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio) +{ + struct request_queue *q = hctx->queue; + struct bfq_data *bfqd = q->elevator->elevator_data; + struct request *free = NULL; + /* + * bfq_bic_lookup grabs the queue_lock: invoke it now and + * store its return value for later use, to avoid nesting + * queue_lock inside the bfqd->lock. We assume that the bic + * returned by bfq_bic_lookup does not go away before + * bfqd->lock is taken. + */ + struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q); + bool ret; + + spin_lock_irq(&bfqd->lock); + + if (bic) + bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf)); + else + bfqd->bio_bfqq = NULL; + bfqd->bio_bic = bic; + + ret = blk_mq_sched_try_merge(q, bio, &free); + + if (free) + blk_mq_free_request(free); + spin_unlock_irq(&bfqd->lock); + + return ret; +} + +static int bfq_request_merge(struct request_queue *q, struct request **req, + struct bio *bio) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct request *__rq; + + __rq = bfq_find_rq_fmerge(bfqd, bio, q); + if (__rq && elv_bio_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_FRONT_MERGE; + } + + return ELEVATOR_NO_MERGE; +} + +static void bfq_request_merged(struct request_queue *q, struct request *req, + enum elv_merge type) +{ + if (type == ELEVATOR_FRONT_MERGE && + rb_prev(&req->rb_node) && + blk_rq_pos(req) < + blk_rq_pos(container_of(rb_prev(&req->rb_node), + struct request, rb_node))) { + struct bfq_queue *bfqq = RQ_BFQQ(req); + struct bfq_data *bfqd = bfqq->bfqd; + struct request *prev, *next_rq; + + /* Reposition request in its sort_list */ + elv_rb_del(&bfqq->sort_list, req); + elv_rb_add(&bfqq->sort_list, req); + + /* Choose next request to be served for bfqq */ + prev = bfqq->next_rq; + next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req, + bfqd->last_position); + bfqq->next_rq = next_rq; + /* + * If next_rq changes, update the queue's budget to fit + * the new request. + */ + if (prev != bfqq->next_rq) + bfq_updated_next_req(bfqd, bfqq); + } +} + +static void bfq_requests_merged(struct request_queue *q, struct request *rq, + struct request *next) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next); + + if (!RB_EMPTY_NODE(&rq->rb_node)) + return; + spin_lock_irq(&bfqq->bfqd->lock); + + /* + * If next and rq belong to the same bfq_queue and next is older + * than rq, then reposition rq in the fifo (by substituting next + * with rq). Otherwise, if next and rq belong to different + * bfq_queues, never reposition rq: in fact, we would have to + * reposition it with respect to next's position in its own fifo, + * which would most certainly be too expensive with respect to + * the benefits. + */ + if (bfqq == next_bfqq && + !list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && + next->fifo_time < rq->fifo_time) { + list_del_init(&rq->queuelist); + list_replace_init(&next->queuelist, &rq->queuelist); + rq->fifo_time = next->fifo_time; + } + + if (bfqq->next_rq == next) + bfqq->next_rq = rq; + + bfq_remove_request(q, next); + + spin_unlock_irq(&bfqq->bfqd->lock); +} + +static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, + struct bio *bio) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + bool is_sync = op_is_sync(bio->bi_opf); + struct bfq_queue *bfqq = bfqd->bio_bfqq; + + /* + * Disallow merge of a sync bio into an async request. + */ + if (is_sync && !rq_is_sync(rq)) + return false; + + /* + * Lookup the bfqq that this bio will be queued with. Allow + * merge only if rq is queued there. + */ + if (!bfqq) + return false; + + return bfqq == RQ_BFQQ(rq); +} + +static void __bfq_set_in_service_queue(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + if (bfqq) { + bfq_mark_bfqq_budget_new(bfqq); + bfq_clear_bfqq_fifo_expire(bfqq); + + bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8; + + bfq_log_bfqq(bfqd, bfqq, + "set_in_service_queue, cur-budget = %d", + bfqq->entity.budget); + } + + bfqd->in_service_queue = bfqq; +} + +/* + * Get and set a new queue for service. + */ +static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfq_get_next_queue(bfqd); + + __bfq_set_in_service_queue(bfqd, bfqq); + return bfqq; +} + +/* + * bfq_default_budget - return the default budget for @bfqq on @bfqd. + * @bfqd: the device descriptor. + * @bfqq: the queue to consider. + * + * We use 3/4 of the @bfqd maximum budget as the default value + * for the max_budget field of the queues. This lets the feedback + * mechanism to start from some middle ground, then the behavior + * of the process will drive the heuristics towards high values, if + * it behaves as a greedy sequential reader, or towards small values + * if it shows a more intermittent behavior. + */ +static unsigned long bfq_default_budget(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + unsigned long budget; + + /* + * When we need an estimate of the peak rate we need to avoid + * to give budgets that are too short due to previous + * measurements. So, in the first 10 assignments use a + * ``safe'' budget value. For such first assignment the value + * of bfqd->budgets_assigned happens to be lower than 194. + * See __bfq_set_in_service_queue for the formula by which + * this field is computed. + */ + if (bfqd->budgets_assigned < 194 && bfqd->bfq_user_max_budget == 0) + budget = bfq_default_max_budget; + else + budget = bfqd->bfq_max_budget; + + return budget - budget / 4; +} + +static void bfq_arm_slice_timer(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfqd->in_service_queue; + struct bfq_io_cq *bic; + u32 sl; + + /* Processes have exited, don't wait. */ + bic = bfqd->in_service_bic; + if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0) + return; + + bfq_mark_bfqq_wait_request(bfqq); + + /* + * We don't want to idle for seeks, but we do want to allow + * fair distribution of slice time for a process doing back-to-back + * seeks. So allow a little bit of time for him to submit a new rq. + */ + sl = bfqd->bfq_slice_idle; + /* + * Grant only minimum idle time if the queue is seeky. + */ + if (BFQQ_SEEKY(bfqq)) + sl = min_t(u64, sl, BFQ_MIN_TT); + + bfqd->last_idling_start = ktime_get(); + hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl), + HRTIMER_MODE_REL); +} + +/* + * Set the maximum time for the in-service queue to consume its + * budget. This prevents seeky processes from lowering the disk + * throughput (always guaranteed with a time slice scheme as in CFQ). + */ +static void bfq_set_budget_timeout(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfqd->in_service_queue; + unsigned int timeout_coeff = bfqq->entity.weight / + bfqq->entity.orig_weight; + + bfqd->last_budget_start = ktime_get(); + + bfq_clear_bfqq_budget_new(bfqq); + bfqq->budget_timeout = jiffies + + bfqd->bfq_timeout * timeout_coeff; + + bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u", + jiffies_to_msecs(bfqd->bfq_timeout * timeout_coeff)); +} + +/* + * Remove request from internal lists. + */ +static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + + /* + * For consistency, the next instruction should have been + * executed after removing the request from the queue and + * dispatching it. We execute instead this instruction before + * bfq_remove_request() (and hence introduce a temporary + * inconsistency), for efficiency. In fact, should this + * dispatch occur for a non in-service bfqq, this anticipated + * increment prevents two counters related to bfqq->dispatched + * from risking to be, first, uselessly decremented, and then + * incremented again when the (new) value of bfqq->dispatched + * happens to be taken into account. + */ + bfqq->dispatched++; + + bfq_remove_request(q, rq); +} + +static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + __bfq_bfqd_reset_in_service(bfqd); + + if (RB_EMPTY_ROOT(&bfqq->sort_list)) + bfq_del_bfqq_busy(bfqd, bfqq, 1); + else + bfq_activate_bfqq(bfqd, bfqq); +} + +/** + * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior. + * @bfqd: device data. + * @bfqq: queue to update. + * @reason: reason for expiration. + * + * Handle the feedback on @bfqq budget at queue expiration. + * See the body for detailed comments. + */ +static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + enum bfqq_expiration reason) +{ + struct request *next_rq; + int budget, min_budget; + + budget = bfqq->max_budget; + min_budget = bfq_min_budget(bfqd); + + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d", + bfqq->entity.budget, bfq_bfqq_budget_left(bfqq)); + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d", + budget, bfq_min_budget(bfqd)); + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d", + bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue)); + + if (bfq_bfqq_sync(bfqq)) { + switch (reason) { + /* + * Caveat: in all the following cases we trade latency + * for throughput. + */ + case BFQQE_TOO_IDLE: + if (budget > min_budget + BFQ_BUDGET_STEP) + budget -= BFQ_BUDGET_STEP; + else + budget = min_budget; + break; + case BFQQE_BUDGET_TIMEOUT: + budget = bfq_default_budget(bfqd, bfqq); + break; + case BFQQE_BUDGET_EXHAUSTED: + /* + * The process still has backlog, and did not + * let either the budget timeout or the disk + * idling timeout expire. Hence it is not + * seeky, has a short thinktime and may be + * happy with a higher budget too. So + * definitely increase the budget of this good + * candidate to boost the disk throughput. + */ + budget = min(budget + 8 * BFQ_BUDGET_STEP, + bfqd->bfq_max_budget); + break; + case BFQQE_NO_MORE_REQUESTS: + /* + * For queues that expire for this reason, it + * is particularly important to keep the + * budget close to the actual service they + * need. Doing so reduces the timestamp + * misalignment problem described in the + * comments in the body of + * __bfq_activate_entity. In fact, suppose + * that a queue systematically expires for + * BFQQE_NO_MORE_REQUESTS and presents a + * new request in time to enjoy timestamp + * back-shifting. The larger the budget of the + * queue is with respect to the service the + * queue actually requests in each service + * slot, the more times the queue can be + * reactivated with the same virtual finish + * time. It follows that, even if this finish + * time is pushed to the system virtual time + * to reduce the consequent timestamp + * misalignment, the queue unjustly enjoys for + * many re-activations a lower finish time + * than all newly activated queues. + * + * The service needed by bfqq is measured + * quite precisely by bfqq->entity.service. + * Since bfqq does not enjoy device idling, + * bfqq->entity.service is equal to the number + * of sectors that the process associated with + * bfqq requested to read/write before waiting + * for request completions, or blocking for + * other reasons. + */ + budget = max_t(int, bfqq->entity.service, min_budget); + break; + default: + return; + } + } else { + /* + * Async queues get always the maximum possible + * budget, as for them we do not care about latency + * (in addition, their ability to dispatch is limited + * by the charging factor). + */ + budget = bfqd->bfq_max_budget; + } + + bfqq->max_budget = budget; + + if (bfqd->budgets_assigned >= bfq_stats_min_budgets && + !bfqd->bfq_user_max_budget) + bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget); + + /* + * If there is still backlog, then assign a new budget, making + * sure that it is large enough for the next request. Since + * the finish time of bfqq must be kept in sync with the + * budget, be sure to call __bfq_bfqq_expire() *after* this + * update. + * + * If there is no backlog, then no need to update the budget; + * it will be updated on the arrival of a new request. + */ + next_rq = bfqq->next_rq; + if (next_rq) + bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(next_rq, bfqq)); + + bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d", + next_rq ? blk_rq_sectors(next_rq) : 0, + bfqq->entity.budget); +} + +static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout) +{ + unsigned long max_budget; + + /* + * The max_budget calculated when autotuning is equal to the + * amount of sectors transferred in timeout at the estimated + * peak rate. To get this value, peak_rate is, first, + * multiplied by 1000, because timeout is measured in ms, + * while peak_rate is measured in sectors/usecs. Then the + * result of this multiplication is right-shifted by + * BFQ_RATE_SHIFT, because peak_rate is equal to the value of + * the peak rate left-shifted by BFQ_RATE_SHIFT. + */ + max_budget = (unsigned long)(peak_rate * 1000 * + timeout >> BFQ_RATE_SHIFT); + + return max_budget; +} + +/* + * In addition to updating the peak rate, checks whether the process + * is "slow", and returns 1 if so. This slow flag is used, in addition + * to the budget timeout, to reduce the amount of service provided to + * seeky processes, and hence reduce their chances to lower the + * throughput. See the code for more details. + */ +static bool bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq, + bool compensate) +{ + u64 bw, usecs, expected, timeout; + ktime_t delta; + int update = 0; + + if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq)) + return false; + + if (compensate) + delta = bfqd->last_idling_start; + else + delta = ktime_get(); + delta = ktime_sub(delta, bfqd->last_budget_start); + usecs = ktime_to_us(delta); + + /* don't use too short time intervals */ + if (usecs < 1000) + return false; + + /* + * Calculate the bandwidth for the last slice. We use a 64 bit + * value to store the peak rate, in sectors per usec in fixed + * point math. We do so to have enough precision in the estimate + * and to avoid overflows. + */ + bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT; + do_div(bw, (unsigned long)usecs); + + timeout = jiffies_to_msecs(bfqd->bfq_timeout); + + /* + * Use only long (> 20ms) intervals to filter out spikes for + * the peak rate estimation. + */ + if (usecs > 20000) { + if (bw > bfqd->peak_rate) { + bfqd->peak_rate = bw; + update = 1; + bfq_log(bfqd, "new peak_rate=%llu", bw); + } + + update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1; + + if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES) + bfqd->peak_rate_samples++; + + if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES && + update && bfqd->bfq_user_max_budget == 0) { + bfqd->bfq_max_budget = + bfq_calc_max_budget(bfqd->peak_rate, + timeout); + bfq_log(bfqd, "new max_budget=%d", + bfqd->bfq_max_budget); + } + } + + /* + * A process is considered ``slow'' (i.e., seeky, so that we + * cannot treat it fairly in the service domain, as it would + * slow down too much the other processes) if, when a slice + * ends for whatever reason, it has received service at a + * rate that would not be high enough to complete the budget + * before the budget timeout expiration. + */ + expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT; + + /* + * Caveat: processes doing IO in the slower disk zones will + * tend to be slow(er) even if not seeky. And the estimated + * peak rate will actually be an average over the disk + * surface. Hence, to not be too harsh with unlucky processes, + * we keep a budget/3 margin of safety before declaring a + * process slow. + */ + return expected > (4 * bfqq->entity.budget) / 3; +} + +/* + * Return the farthest past time instant according to jiffies + * macros. + */ +static unsigned long bfq_smallest_from_now(void) +{ + return jiffies - MAX_JIFFY_OFFSET; +} + +/** + * bfq_bfqq_expire - expire a queue. + * @bfqd: device owning the queue. + * @bfqq: the queue to expire. + * @compensate: if true, compensate for the time spent idling. + * @reason: the reason causing the expiration. + * + * + * If the process associated with the queue is slow (i.e., seeky), or + * in case of budget timeout, or, finally, if it is async, we + * artificially charge it an entire budget (independently of the + * actual service it received). As a consequence, the queue will get + * higher timestamps than the correct ones upon reactivation, and + * hence it will be rescheduled as if it had received more service + * than what it actually received. In the end, this class of processes + * will receive less service in proportion to how slowly they consume + * their budgets (and hence how seriously they tend to lower the + * throughput). + * + * In contrast, when a queue expires because it has been idling for + * too much or because it exhausted its budget, we do not touch the + * amount of service it has received. Hence when the queue will be + * reactivated and its timestamps updated, the latter will be in sync + * with the actual service received by the queue until expiration. + * + * Charging a full budget to the first type of queues and the exact + * service to the others has the effect of using the WF2Q+ policy to + * schedule the former on a timeslice basis, without violating the + * service domain guarantees of the latter. + */ +static void bfq_bfqq_expire(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + bool compensate, + enum bfqq_expiration reason) +{ + bool slow; + int ref; + + /* + * Update device peak rate for autotuning and check whether the + * process is slow (see bfq_update_peak_rate). + */ + slow = bfq_update_peak_rate(bfqd, bfqq, compensate); + + /* + * As above explained, 'punish' slow (i.e., seeky), timed-out + * and async queues, to favor sequential sync workloads. + */ + if (slow || reason == BFQQE_BUDGET_TIMEOUT) + bfq_bfqq_charge_full_budget(bfqq); + + if (reason == BFQQE_TOO_IDLE && + bfqq->entity.service <= 2 * bfqq->entity.budget / 10) + bfq_clear_bfqq_IO_bound(bfqq); + + bfq_log_bfqq(bfqd, bfqq, + "expire (%d, slow %d, num_disp %d, idle_win %d)", reason, + slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq)); + + /* + * Increase, decrease or leave budget unchanged according to + * reason. + */ + __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); + ref = bfqq->ref; + __bfq_bfqq_expire(bfqd, bfqq); + + /* mark bfqq as waiting a request only if a bic still points to it */ + if (ref > 1 && !bfq_bfqq_busy(bfqq) && + reason != BFQQE_BUDGET_TIMEOUT && + reason != BFQQE_BUDGET_EXHAUSTED) + bfq_mark_bfqq_non_blocking_wait_rq(bfqq); +} + +/* + * Budget timeout is not implemented through a dedicated timer, but + * just checked on request arrivals and completions, as well as on + * idle timer expirations. + */ +static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq) +{ + if (bfq_bfqq_budget_new(bfqq) || + time_is_after_jiffies(bfqq->budget_timeout)) + return false; + return true; +} + +/* + * If we expire a queue that is actively waiting (i.e., with the + * device idled) for the arrival of a new request, then we may incur + * the timestamp misalignment problem described in the body of the + * function __bfq_activate_entity. Hence we return true only if this + * condition does not hold, or if the queue is slow enough to deserve + * only to be kicked off for preserving a high throughput. + */ +static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq) +{ + bfq_log_bfqq(bfqq->bfqd, bfqq, + "may_budget_timeout: wait_request %d left %d timeout %d", + bfq_bfqq_wait_request(bfqq), + bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3, + bfq_bfqq_budget_timeout(bfqq)); + + return (!bfq_bfqq_wait_request(bfqq) || + bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3) + && + bfq_bfqq_budget_timeout(bfqq); +} + +/* + * For a queue that becomes empty, device idling is allowed only if + * this function returns true for the queue. And this function returns + * true only if idling is beneficial for throughput. + */ +static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; + bool idling_boosts_thr; + + if (bfqd->strict_guarantees) + return true; + + /* + * The value of the next variable is computed considering that + * idling is usually beneficial for the throughput if: + * (a) the device is not NCQ-capable, or + * (b) regardless of the presence of NCQ, the request pattern + * for bfqq is I/O-bound (possible throughput losses + * caused by granting idling to seeky queues are mitigated + * by the fact that, in all scenarios where boosting + * throughput is the best thing to do, i.e., in all + * symmetric scenarios, only a minimal idle time is + * allowed to seeky queues). + */ + idling_boosts_thr = !bfqd->hw_tag || bfq_bfqq_IO_bound(bfqq); + + /* + * We have now the components we need to compute the return + * value of the function, which is true only if both the + * following conditions hold: + * 1) bfqq is sync, because idling make sense only for sync queues; + * 2) idling boosts the throughput. + */ + return bfq_bfqq_sync(bfqq) && idling_boosts_thr; +} + +/* + * If the in-service queue is empty but the function bfq_bfqq_may_idle + * returns true, then: + * 1) the queue must remain in service and cannot be expired, and + * 2) the device must be idled to wait for the possible arrival of a new + * request for the queue. + * See the comments on the function bfq_bfqq_may_idle for the reasons + * why performing device idling is the best choice to boost the throughput + * and preserve service guarantees when bfq_bfqq_may_idle itself + * returns true. + */ +static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; + + return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 && + bfq_bfqq_may_idle(bfqq); +} + +/* + * Select a queue for service. If we have a current queue in service, + * check whether to continue servicing it, or retrieve and set a new one. + */ +static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq; + struct request *next_rq; + enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT; + + bfqq = bfqd->in_service_queue; + if (!bfqq) + goto new_queue; + + bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue"); + + if (bfq_may_expire_for_budg_timeout(bfqq) && + !bfq_bfqq_wait_request(bfqq) && + !bfq_bfqq_must_idle(bfqq)) + goto expire; + +check_queue: + /* + * This loop is rarely executed more than once. Even when it + * happens, it is much more convenient to re-execute this loop + * than to return NULL and trigger a new dispatch to get a + * request served. + */ + next_rq = bfqq->next_rq; + /* + * If bfqq has requests queued and it has enough budget left to + * serve them, keep the queue, otherwise expire it. + */ + if (next_rq) { + if (bfq_serv_to_charge(next_rq, bfqq) > + bfq_bfqq_budget_left(bfqq)) { + /* + * Expire the queue for budget exhaustion, + * which makes sure that the next budget is + * enough to serve the next request, even if + * it comes from the fifo expired path. + */ + reason = BFQQE_BUDGET_EXHAUSTED; + goto expire; + } else { + /* + * The idle timer may be pending because we may + * not disable disk idling even when a new request + * arrives. + */ + if (bfq_bfqq_wait_request(bfqq)) { + /* + * If we get here: 1) at least a new request + * has arrived but we have not disabled the + * timer because the request was too small, + * 2) then the block layer has unplugged + * the device, causing the dispatch to be + * invoked. + * + * Since the device is unplugged, now the + * requests are probably large enough to + * provide a reasonable throughput. + * So we disable idling. + */ + bfq_clear_bfqq_wait_request(bfqq); + hrtimer_try_to_cancel(&bfqd->idle_slice_timer); + } + goto keep_queue; + } + } + + /* + * No requests pending. However, if the in-service queue is idling + * for a new request, or has requests waiting for a completion and + * may idle after their completion, then keep it anyway. + */ + if (bfq_bfqq_wait_request(bfqq) || + (bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) { + bfqq = NULL; + goto keep_queue; + } + + reason = BFQQE_NO_MORE_REQUESTS; +expire: + bfq_bfqq_expire(bfqd, bfqq, false, reason); +new_queue: + bfqq = bfq_set_in_service_queue(bfqd); + if (bfqq) { + bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue"); + goto check_queue; + } +keep_queue: + if (bfqq) + bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue"); + else + bfq_log(bfqd, "select_queue: no queue returned"); + + return bfqq; +} + +/* + * Dispatch next request from bfqq. + */ +static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + struct request *rq = bfqq->next_rq; + unsigned long service_to_charge; + + service_to_charge = bfq_serv_to_charge(rq, bfqq); + + bfq_bfqq_served(bfqq, service_to_charge); + + bfq_dispatch_remove(bfqd->queue, rq); + + if (!bfqd->in_service_bic) { + atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount); + bfqd->in_service_bic = RQ_BIC(rq); + } + + /* + * Expire bfqq, pretending that its budget expired, if bfqq + * belongs to CLASS_IDLE and other queues are waiting for + * service. + */ + if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq)) + goto expire; + + return rq; + +expire: + bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED); + return rq; +} + +static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) +{ + struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; + + /* + * Avoiding lock: a race on bfqd->busy_queues should cause at + * most a call to dispatch for nothing + */ + return !list_empty_careful(&bfqd->dispatch) || + bfqd->busy_queues > 0; +} + +static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) +{ + struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; + struct request *rq = NULL; + struct bfq_queue *bfqq = NULL; + + if (!list_empty(&bfqd->dispatch)) { + rq = list_first_entry(&bfqd->dispatch, struct request, + queuelist); + list_del_init(&rq->queuelist); + + bfqq = RQ_BFQQ(rq); + + if (bfqq) { + /* + * Increment counters here, because this + * dispatch does not follow the standard + * dispatch flow (where counters are + * incremented) + */ + bfqq->dispatched++; + + goto inc_in_driver_start_rq; + } + + /* + * We exploit the put_rq_private hook to decrement + * rq_in_driver, but put_rq_private will not be + * invoked on this request. So, to avoid unbalance, + * just start this request, without incrementing + * rq_in_driver. As a negative consequence, + * rq_in_driver is deceptively lower than it should be + * while this request is in service. This may cause + * bfq_schedule_dispatch to be invoked uselessly. + * + * As for implementing an exact solution, the + * put_request hook, if defined, is probably invoked + * also on this request. So, by exploiting this hook, + * we could 1) increment rq_in_driver here, and 2) + * decrement it in put_request. Such a solution would + * let the value of the counter be always accurate, + * but it would entail using an extra interface + * function. This cost seems higher than the benefit, + * being the frequency of non-elevator-private + * requests very low. + */ + goto start_rq; + } + + bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues); + + if (bfqd->busy_queues == 0) + goto exit; + + /* + * Force device to serve one request at a time if + * strict_guarantees is true. Forcing this service scheme is + * currently the ONLY way to guarantee that the request + * service order enforced by the scheduler is respected by a + * queueing device. Otherwise the device is free even to make + * some unlucky request wait for as long as the device + * wishes. + * + * Of course, serving one request at at time may cause loss of + * throughput. + */ + if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0) + goto exit; + + bfqq = bfq_select_queue(bfqd); + if (!bfqq) + goto exit; + + rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq); + + if (rq) { +inc_in_driver_start_rq: + bfqd->rq_in_driver++; +start_rq: + rq->rq_flags |= RQF_STARTED; + } +exit: + return rq; +} + +static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) +{ + struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; + struct request *rq; + + spin_lock_irq(&bfqd->lock); + rq = __bfq_dispatch_request(hctx); + spin_unlock_irq(&bfqd->lock); + + return rq; +} + +/* + * Task holds one reference to the queue, dropped when task exits. Each rq + * in-flight on this queue also holds a reference, dropped when rq is freed. + * + * Scheduler lock must be held here. Recall not to use bfqq after calling + * this function on it. + */ +static void bfq_put_queue(struct bfq_queue *bfqq) +{ + if (bfqq->bfqd) + bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d", + bfqq, bfqq->ref); + + bfqq->ref--; + if (bfqq->ref) + return; + + kmem_cache_free(bfq_pool, bfqq); +} + +static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + if (bfqq == bfqd->in_service_queue) { + __bfq_bfqq_expire(bfqd, bfqq); + bfq_schedule_dispatch(bfqd); + } + + bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref); + + bfq_put_queue(bfqq); /* release process reference */ +} + +static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync) +{ + struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); + struct bfq_data *bfqd; + + if (bfqq) + bfqd = bfqq->bfqd; /* NULL if scheduler already exited */ + + if (bfqq && bfqd) { + unsigned long flags; + + spin_lock_irqsave(&bfqd->lock, flags); + bfq_exit_bfqq(bfqd, bfqq); + bic_set_bfqq(bic, NULL, is_sync); + spin_unlock_irq(&bfqd->lock); + } +} + +static void bfq_exit_icq(struct io_cq *icq) +{ + struct bfq_io_cq *bic = icq_to_bic(icq); + + bfq_exit_icq_bfqq(bic, true); + bfq_exit_icq_bfqq(bic, false); +} + +/* + * Update the entity prio values; note that the new values will not + * be used until the next (re)activation. + */ +static void +bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic) +{ + struct task_struct *tsk = current; + int ioprio_class; + struct bfq_data *bfqd = bfqq->bfqd; + + if (!bfqd) + return; + + ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); + switch (ioprio_class) { + default: + dev_err(bfqq->bfqd->queue->backing_dev_info->dev, + "bfq: bad prio class %d\n", ioprio_class); + case IOPRIO_CLASS_NONE: + /* + * No prio set, inherit CPU scheduling settings. + */ + bfqq->new_ioprio = task_nice_ioprio(tsk); + bfqq->new_ioprio_class = task_nice_ioclass(tsk); + break; + case IOPRIO_CLASS_RT: + bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); + bfqq->new_ioprio_class = IOPRIO_CLASS_RT; + break; + case IOPRIO_CLASS_BE: + bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); + bfqq->new_ioprio_class = IOPRIO_CLASS_BE; + break; + case IOPRIO_CLASS_IDLE: + bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE; + bfqq->new_ioprio = 7; + bfq_clear_bfqq_idle_window(bfqq); + break; + } + + if (bfqq->new_ioprio >= IOPRIO_BE_NR) { + pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n", + bfqq->new_ioprio); + bfqq->new_ioprio = IOPRIO_BE_NR; + } + + bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio); + bfqq->entity.prio_changed = 1; +} + +static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) +{ + struct bfq_data *bfqd = bic_to_bfqd(bic); + struct bfq_queue *bfqq; + int ioprio = bic->icq.ioc->ioprio; + + /* + * This condition may trigger on a newly created bic, be sure to + * drop the lock before returning. + */ + if (unlikely(!bfqd) || likely(bic->ioprio == ioprio)) + return; + + bic->ioprio = ioprio; + + bfqq = bic_to_bfqq(bic, false); + if (bfqq) { + /* release process reference on this queue */ + bfq_put_queue(bfqq); + bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic); + bic_set_bfqq(bic, bfqq, false); + } + + bfqq = bic_to_bfqq(bic, true); + if (bfqq) + bfq_set_next_ioprio_data(bfqq, bic); +} + +static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, + struct bfq_io_cq *bic, pid_t pid, int is_sync) +{ + RB_CLEAR_NODE(&bfqq->entity.rb_node); + INIT_LIST_HEAD(&bfqq->fifo); + + bfqq->ref = 0; + bfqq->bfqd = bfqd; + + if (bic) + bfq_set_next_ioprio_data(bfqq, bic); + + if (is_sync) { + if (!bfq_class_idle(bfqq)) + bfq_mark_bfqq_idle_window(bfqq); + bfq_mark_bfqq_sync(bfqq); + } else + bfq_clear_bfqq_sync(bfqq); + + /* set end request to minus infinity from now */ + bfqq->ttime.last_end_request = ktime_get_ns() + 1; + + bfq_mark_bfqq_IO_bound(bfqq); + + bfqq->pid = pid; + + /* Tentative initial value to trade off between thr and lat */ + bfqq->max_budget = bfq_default_budget(bfqd, bfqq); + bfqq->budget_timeout = bfq_smallest_from_now(); + bfqq->pid = pid; + + /* first request is almost certainly seeky */ + bfqq->seek_history = 1; +} + +static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, + int ioprio_class, int ioprio) +{ + switch (ioprio_class) { + case IOPRIO_CLASS_RT: + return &async_bfqq[0][ioprio]; + case IOPRIO_CLASS_NONE: + ioprio = IOPRIO_NORM; + /* fall through */ + case IOPRIO_CLASS_BE: + return &async_bfqq[1][ioprio]; + case IOPRIO_CLASS_IDLE: + return &async_idle_bfqq; + default: + return NULL; + } +} + +static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, + struct bio *bio, bool is_sync, + struct bfq_io_cq *bic) +{ + const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio); + const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); + struct bfq_queue **async_bfqq = NULL; + struct bfq_queue *bfqq; + + rcu_read_lock(); + + if (!is_sync) { + async_bfqq = bfq_async_queue_prio(bfqd, ioprio_class, + ioprio); + bfqq = *async_bfqq; + if (bfqq) + goto out; + } + + bfqq = kmem_cache_alloc_node(bfq_pool, + GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN, + bfqd->queue->node); + + if (bfqq) { + bfq_init_bfqq(bfqd, bfqq, bic, current->pid, + is_sync); + bfq_init_entity(&bfqq->entity); + bfq_log_bfqq(bfqd, bfqq, "allocated"); + } else { + bfqq = &bfqd->oom_bfqq; + bfq_log_bfqq(bfqd, bfqq, "using oom bfqq"); + goto out; + } + + /* + * Pin the queue now that it's allocated, scheduler exit will + * prune it. + */ + if (async_bfqq) { + bfqq->ref++; + bfq_log_bfqq(bfqd, bfqq, + "get_queue, bfqq not in async: %p, %d", + bfqq, bfqq->ref); + *async_bfqq = bfqq; + } + +out: + bfqq->ref++; /* get a process reference to this queue */ + bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref); + rcu_read_unlock(); + return bfqq; +} + +static void bfq_update_io_thinktime(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + struct bfq_ttime *ttime = &bfqq->ttime; + u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request; + + elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle); + + ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8; + ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8); + ttime->ttime_mean = div64_ul(ttime->ttime_total + 128, + ttime->ttime_samples); +} + +static void +bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, + struct request *rq) +{ + sector_t sdist = 0; + + if (bfqq->last_request_pos) { + if (bfqq->last_request_pos < blk_rq_pos(rq)) + sdist = blk_rq_pos(rq) - bfqq->last_request_pos; + else + sdist = bfqq->last_request_pos - blk_rq_pos(rq); + } + + bfqq->seek_history <<= 1; + bfqq->seek_history |= sdist > BFQQ_SEEK_THR && + (!blk_queue_nonrot(bfqd->queue) || + blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT); +} + +/* + * Disable idle window if the process thinks too long or seeks so much that + * it doesn't matter. + */ +static void bfq_update_idle_window(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct bfq_io_cq *bic) +{ + int enable_idle; + + /* Don't idle for async or idle io prio class. */ + if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq)) + return; + + enable_idle = bfq_bfqq_idle_window(bfqq); + + if (atomic_read(&bic->icq.ioc->active_ref) == 0 || + bfqd->bfq_slice_idle == 0 || + (bfqd->hw_tag && BFQQ_SEEKY(bfqq))) + enable_idle = 0; + else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) { + if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle) + enable_idle = 0; + else + enable_idle = 1; + } + bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d", + enable_idle); + + if (enable_idle) + bfq_mark_bfqq_idle_window(bfqq); + else + bfq_clear_bfqq_idle_window(bfqq); +} + +/* + * Called when a new fs request (rq) is added to bfqq. Check if there's + * something we should do about it. + */ +static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, + struct request *rq) +{ + struct bfq_io_cq *bic = RQ_BIC(rq); + + if (rq->cmd_flags & REQ_META) + bfqq->meta_pending++; + + bfq_update_io_thinktime(bfqd, bfqq); + bfq_update_io_seektime(bfqd, bfqq, rq); + if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 || + !BFQQ_SEEKY(bfqq)) + bfq_update_idle_window(bfqd, bfqq, bic); + + bfq_log_bfqq(bfqd, bfqq, + "rq_enqueued: idle_window=%d (seeky %d)", + bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq)); + + bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); + + if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) { + bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 && + blk_rq_sectors(rq) < 32; + bool budget_timeout = bfq_bfqq_budget_timeout(bfqq); + + /* + * There is just this request queued: if the request + * is small and the queue is not to be expired, then + * just exit. + * + * In this way, if the device is being idled to wait + * for a new request from the in-service queue, we + * avoid unplugging the device and committing the + * device to serve just a small request. On the + * contrary, we wait for the block layer to decide + * when to unplug the device: hopefully, new requests + * will be merged to this one quickly, then the device + * will be unplugged and larger requests will be + * dispatched. + */ + if (small_req && !budget_timeout) + return; + + /* + * A large enough request arrived, or the queue is to + * be expired: in both cases disk idling is to be + * stopped, so clear wait_request flag and reset + * timer. + */ + bfq_clear_bfqq_wait_request(bfqq); + hrtimer_try_to_cancel(&bfqd->idle_slice_timer); + + /* + * The queue is not empty, because a new request just + * arrived. Hence we can safely expire the queue, in + * case of budget timeout, without risking that the + * timestamps of the queue are not updated correctly. + * See [1] for more details. + */ + if (budget_timeout) + bfq_bfqq_expire(bfqd, bfqq, false, + BFQQE_BUDGET_TIMEOUT); + } +} + +static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + + bfq_add_request(rq); + + rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)]; + list_add_tail(&rq->queuelist, &bfqq->fifo); + + bfq_rq_enqueued(bfqd, bfqq, rq); +} + +static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, + bool at_head) +{ + struct request_queue *q = hctx->queue; + struct bfq_data *bfqd = q->elevator->elevator_data; + + spin_lock_irq(&bfqd->lock); + if (blk_mq_sched_try_insert_merge(q, rq)) { + spin_unlock_irq(&bfqd->lock); + return; + } + + spin_unlock_irq(&bfqd->lock); + + blk_mq_sched_request_inserted(rq); + + spin_lock_irq(&bfqd->lock); + if (at_head || blk_rq_is_passthrough(rq)) { + if (at_head) + list_add(&rq->queuelist, &bfqd->dispatch); + else + list_add_tail(&rq->queuelist, &bfqd->dispatch); + } else { + __bfq_insert_request(bfqd, rq); + + if (rq_mergeable(rq)) { + elv_rqhash_add(q, rq); + if (!q->last_merge) + q->last_merge = rq; + } + } + + spin_unlock_irq(&bfqd->lock); +} + +static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx, + struct list_head *list, bool at_head) +{ + while (!list_empty(list)) { + struct request *rq; + + rq = list_first_entry(list, struct request, queuelist); + list_del_init(&rq->queuelist); + bfq_insert_request(hctx, rq, at_head); + } +} + +static void bfq_update_hw_tag(struct bfq_data *bfqd) +{ + bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver, + bfqd->rq_in_driver); + + if (bfqd->hw_tag == 1) + return; + + /* + * This sample is valid if the number of outstanding requests + * is large enough to allow a queueing behavior. Note that the + * sum is not exact, as it's not taking into account deactivated + * requests. + */ + if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) + return; + + if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) + return; + + bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD; + bfqd->max_rq_in_driver = 0; + bfqd->hw_tag_samples = 0; +} + +static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) +{ + bfq_update_hw_tag(bfqd); + + bfqd->rq_in_driver--; + bfqq->dispatched--; + + bfqq->ttime.last_end_request = ktime_get_ns(); + + /* + * If this is the in-service queue, check if it needs to be expired, + * or if we want to idle in case it has no pending requests. + */ + if (bfqd->in_service_queue == bfqq) { + if (bfq_bfqq_budget_new(bfqq)) + bfq_set_budget_timeout(bfqd); + + if (bfq_bfqq_must_idle(bfqq)) { + bfq_arm_slice_timer(bfqd); + return; + } else if (bfq_may_expire_for_budg_timeout(bfqq)) + bfq_bfqq_expire(bfqd, bfqq, false, + BFQQE_BUDGET_TIMEOUT); + else if (RB_EMPTY_ROOT(&bfqq->sort_list) && + (bfqq->dispatched == 0 || + !bfq_bfqq_may_idle(bfqq))) + bfq_bfqq_expire(bfqd, bfqq, false, + BFQQE_NO_MORE_REQUESTS); + } +} + +static void bfq_put_rq_priv_body(struct bfq_queue *bfqq) +{ + bfqq->allocated--; + + bfq_put_queue(bfqq); +} + +static void bfq_put_rq_private(struct request_queue *q, struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_data *bfqd = bfqq->bfqd; + + + if (likely(rq->rq_flags & RQF_STARTED)) { + unsigned long flags; + + spin_lock_irqsave(&bfqd->lock, flags); + + bfq_completed_request(bfqq, bfqd); + bfq_put_rq_priv_body(bfqq); + + spin_unlock_irqrestore(&bfqd->lock, flags); + } else { + /* + * Request rq may be still/already in the scheduler, + * in which case we need to remove it. And we cannot + * defer such a check and removal, to avoid + * inconsistencies in the time interval from the end + * of this function to the start of the deferred work. + * This situation seems to occur only in process + * context, as a consequence of a merge. In the + * current version of the code, this implies that the + * lock is held. + */ + + if (!RB_EMPTY_NODE(&rq->rb_node)) + bfq_remove_request(q, rq); + bfq_put_rq_priv_body(bfqq); + } + + rq->elv.priv[0] = NULL; + rq->elv.priv[1] = NULL; +} + +/* + * Allocate bfq data structures associated with this request. + */ +static int bfq_get_rq_private(struct request_queue *q, struct request *rq, + struct bio *bio) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq); + const int is_sync = rq_is_sync(rq); + struct bfq_queue *bfqq; + + spin_lock_irq(&bfqd->lock); + + bfq_check_ioprio_change(bic, bio); + + if (!bic) + goto queue_fail; + + bfqq = bic_to_bfqq(bic, is_sync); + if (!bfqq || bfqq == &bfqd->oom_bfqq) { + if (bfqq) + bfq_put_queue(bfqq); + bfqq = bfq_get_queue(bfqd, bio, is_sync, bic); + bic_set_bfqq(bic, bfqq, is_sync); + } + + bfqq->allocated++; + bfqq->ref++; + bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d", + rq, bfqq, bfqq->ref); + + rq->elv.priv[0] = bic; + rq->elv.priv[1] = bfqq; + + spin_unlock_irq(&bfqd->lock); + + return 0; + +queue_fail: + spin_unlock_irq(&bfqd->lock); + + return 1; +} + +static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; + enum bfqq_expiration reason; + unsigned long flags; + + spin_lock_irqsave(&bfqd->lock, flags); + bfq_clear_bfqq_wait_request(bfqq); + + if (bfqq != bfqd->in_service_queue) { + spin_unlock_irqrestore(&bfqd->lock, flags); + return; + } + + if (bfq_bfqq_budget_timeout(bfqq)) + /* + * Also here the queue can be safely expired + * for budget timeout without wasting + * guarantees + */ + reason = BFQQE_BUDGET_TIMEOUT; + else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0) + /* + * The queue may not be empty upon timer expiration, + * because we may not disable the timer when the + * first request of the in-service queue arrives + * during disk idling. + */ + reason = BFQQE_TOO_IDLE; + else + goto schedule_dispatch; + + bfq_bfqq_expire(bfqd, bfqq, true, reason); + +schedule_dispatch: + spin_unlock_irqrestore(&bfqd->lock, flags); + bfq_schedule_dispatch(bfqd); +} + +/* + * Handler of the expiration of the timer running if the in-service queue + * is idling inside its time slice. + */ +static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer) +{ + struct bfq_data *bfqd = container_of(timer, struct bfq_data, + idle_slice_timer); + struct bfq_queue *bfqq = bfqd->in_service_queue; + + /* + * Theoretical race here: the in-service queue can be NULL or + * different from the queue that was idling if a new request + * arrives for the current queue and there is a full dispatch + * cycle that changes the in-service queue. This can hardly + * happen, but in the worst case we just expire a queue too + * early. + */ + if (bfqq) + bfq_idle_slice_timer_body(bfqq); + + return HRTIMER_NORESTART; +} + +static void __bfq_put_async_bfqq(struct bfq_data *bfqd, + struct bfq_queue **bfqq_ptr) +{ + struct bfq_queue *bfqq = *bfqq_ptr; + + bfq_log(bfqd, "put_async_bfqq: %p", bfqq); + if (bfqq) { + bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d", + bfqq, bfqq->ref); + bfq_put_queue(bfqq); + *bfqq_ptr = NULL; + } +} + +/* + * Release the extra reference of the async queues as the device + * goes away. + */ +static void bfq_put_async_queues(struct bfq_data *bfqd) +{ + int i, j; + + for (i = 0; i < 2; i++) + for (j = 0; j < IOPRIO_BE_NR; j++) + __bfq_put_async_bfqq(bfqd, &async_bfqq[i][j]); + + __bfq_put_async_bfqq(bfqd, &async_idle_bfqq); +} + +static void bfq_exit_queue(struct elevator_queue *e) +{ + struct bfq_data *bfqd = e->elevator_data; + struct bfq_queue *bfqq, *n; + + hrtimer_cancel(&bfqd->idle_slice_timer); + + spin_lock_irq(&bfqd->lock); + list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list) + bfq_deactivate_bfqq(bfqd, bfqq, false); + bfq_put_async_queues(bfqd); + spin_unlock_irq(&bfqd->lock); + + hrtimer_cancel(&bfqd->idle_slice_timer); + + kfree(bfqd); +} + +static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) +{ + struct bfq_data *bfqd; + struct elevator_queue *eq; + int i; + + eq = elevator_alloc(q, e); + if (!eq) + return -ENOMEM; + + bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node); + if (!bfqd) { + kobject_put(&eq->kobj); + return -ENOMEM; + } + eq->elevator_data = bfqd; + + /* + * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. + * Grab a permanent reference to it, so that the normal code flow + * will not attempt to free it. + */ + bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0); + bfqd->oom_bfqq.ref++; + bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; + bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE; + bfqd->oom_bfqq.entity.new_weight = + bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio); + /* + * Trigger weight initialization, according to ioprio, at the + * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio + * class won't be changed any more. + */ + bfqd->oom_bfqq.entity.prio_changed = 1; + + bfqd->queue = q; + + for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) + bfqd->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; + + hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC, + HRTIMER_MODE_REL); + bfqd->idle_slice_timer.function = bfq_idle_slice_timer; + + INIT_LIST_HEAD(&bfqd->active_list); + INIT_LIST_HEAD(&bfqd->idle_list); + + bfqd->hw_tag = -1; + + bfqd->bfq_max_budget = bfq_default_max_budget; + + bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0]; + bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1]; + bfqd->bfq_back_max = bfq_back_max; + bfqd->bfq_back_penalty = bfq_back_penalty; + bfqd->bfq_slice_idle = bfq_slice_idle; + bfqd->bfq_class_idle_last_service = 0; + bfqd->bfq_timeout = bfq_timeout; + + bfqd->bfq_requests_within_timer = 120; + + spin_lock_init(&bfqd->lock); + INIT_LIST_HEAD(&bfqd->dispatch); + + q->elevator = eq; + + return 0; +} + +static void bfq_slab_kill(void) +{ + kmem_cache_destroy(bfq_pool); +} + +static int __init bfq_slab_setup(void) +{ + bfq_pool = KMEM_CACHE(bfq_queue, 0); + if (!bfq_pool) + return -ENOMEM; + return 0; +} + +static ssize_t bfq_var_show(unsigned int var, char *page) +{ + return sprintf(page, "%u\n", var); +} + +static ssize_t bfq_var_store(unsigned long *var, const char *page, + size_t count) +{ + unsigned long new_val; + int ret = kstrtoul(page, 10, &new_val); + + if (ret == 0) + *var = new_val; + + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + u64 __data = __VAR; \ + if (__CONV == 1) \ + __data = jiffies_to_msecs(__data); \ + else if (__CONV == 2) \ + __data = div_u64(__data, NSEC_PER_MSEC); \ + return bfq_var_show(__data, (page)); \ +} +SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2); +SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2); +SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0); +SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0); +SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2); +SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0); +SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1); +SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0); +#undef SHOW_FUNCTION + +#define USEC_SHOW_FUNCTION(__FUNC, __VAR) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + u64 __data = __VAR; \ + __data = div_u64(__data, NSEC_PER_USEC); \ + return bfq_var_show(__data, (page)); \ +} +USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle); +#undef USEC_SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t \ +__FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + unsigned long uninitialized_var(__data); \ + int ret = bfq_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV == 1) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else if (__CONV == 2) \ + *(__PTR) = (u64)__data * NSEC_PER_MSEC; \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1, + INT_MAX, 2); +STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1, + INT_MAX, 2); +STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0); +STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1, + INT_MAX, 0); +STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2); +#undef STORE_FUNCTION + +#define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + unsigned long uninitialized_var(__data); \ + int ret = bfq_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + *(__PTR) = (u64)__data * NSEC_PER_USEC; \ + return ret; \ +} +USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0, + UINT_MAX); +#undef USEC_STORE_FUNCTION + +static unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd) +{ + u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout); + + if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES) + return bfq_calc_max_budget(bfqd->peak_rate, timeout); + else + return bfq_default_max_budget; +} + +static ssize_t bfq_max_budget_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data == 0) + bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); + else { + if (__data > INT_MAX) + __data = INT_MAX; + bfqd->bfq_max_budget = __data; + } + + bfqd->bfq_user_max_budget = __data; + + return ret; +} + +/* + * Leaving this name to preserve name compatibility with cfq + * parameters, but this timeout is used for both sync and async. + */ +static ssize_t bfq_timeout_sync_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data < 1) + __data = 1; + else if (__data > INT_MAX) + __data = INT_MAX; + + bfqd->bfq_timeout = msecs_to_jiffies(__data); + if (bfqd->bfq_user_max_budget == 0) + bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); + + return ret; +} + +static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data > 1) + __data = 1; + if (!bfqd->strict_guarantees && __data == 1 + && bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC) + bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC; + + bfqd->strict_guarantees = __data; + + return ret; +} + +#define BFQ_ATTR(name) \ + __ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store) + +static struct elv_fs_entry bfq_attrs[] = { + BFQ_ATTR(fifo_expire_sync), + BFQ_ATTR(fifo_expire_async), + BFQ_ATTR(back_seek_max), + BFQ_ATTR(back_seek_penalty), + BFQ_ATTR(slice_idle), + BFQ_ATTR(slice_idle_us), + BFQ_ATTR(max_budget), + BFQ_ATTR(timeout_sync), + BFQ_ATTR(strict_guarantees), + __ATTR_NULL +}; + +static struct elevator_type iosched_bfq_mq = { + .ops.mq = { + .get_rq_priv = bfq_get_rq_private, + .put_rq_priv = bfq_put_rq_private, + .exit_icq = bfq_exit_icq, + .insert_requests = bfq_insert_requests, + .dispatch_request = bfq_dispatch_request, + .next_request = elv_rb_latter_request, + .former_request = elv_rb_former_request, + .allow_merge = bfq_allow_bio_merge, + .bio_merge = bfq_bio_merge, + .request_merge = bfq_request_merge, + .requests_merged = bfq_requests_merged, + .request_merged = bfq_request_merged, + .has_work = bfq_has_work, + .init_sched = bfq_init_queue, + .exit_sched = bfq_exit_queue, + }, + + .uses_mq = true, + .icq_size = sizeof(struct bfq_io_cq), + .icq_align = __alignof__(struct bfq_io_cq), + .elevator_attrs = bfq_attrs, + .elevator_name = "bfq", + .elevator_owner = THIS_MODULE, +}; + +static int __init bfq_init(void) +{ + int ret; + + ret = -ENOMEM; + if (bfq_slab_setup()) + goto err_pol_unreg; + + ret = elv_register(&iosched_bfq_mq); + if (ret) + goto err_pol_unreg; + + return 0; + +err_pol_unreg: + return ret; +} + +static void __exit bfq_exit(void) +{ + elv_unregister(&iosched_bfq_mq); + bfq_slab_kill(); +} + +module_init(bfq_init); +module_exit(bfq_exit); + +MODULE_AUTHOR("Paolo Valente"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler"); |