// SPDX-License-Identifier: GPL-2.0
/*
* DAMON-based page reclamation
*
* Author: SeongJae Park <sj@kernel.org>
*/
#define pr_fmt(fmt) "damon-reclaim: " fmt
#include <linux/damon.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/workqueue.h>
#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "damon_reclaim."
/*
* Enable or disable DAMON_RECLAIM.
*
* You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``.
* Setting it as ``N`` disables DAMON_RECLAIM. Note that DAMON_RECLAIM could
* do no real monitoring and reclamation due to the watermarks-based activation
* condition. Refer to below descriptions for the watermarks parameter for
* this.
*/
static bool enabled __read_mostly;
module_param(enabled, bool, 0600);
/*
* Time threshold for cold memory regions identification in microseconds.
*
* If a memory region is not accessed for this or longer time, DAMON_RECLAIM
* identifies the region as cold, and reclaims. 120 seconds by default.
*/
static unsigned long min_age __read_mostly = 120000000;
module_param(min_age, ulong, 0600);
/*
* Limit of time for trying the reclamation in milliseconds.
*
* DAMON_RECLAIM tries to use only up to this time within a time window
* (quota_reset_interval_ms) for trying reclamation of cold pages. This can be
* used for limiting CPU consumption of DAMON_RECLAIM. If the value is zero,
* the limit is disabled.
*
* 10 ms by default.
*/
static unsigned long quota_ms __read_mostly = 10;
module_param(quota_ms, ulong, 0600);
/*
* Limit of size of memory for the reclamation in bytes.
*
* DAMON_RECLAIM charges amount of memory which it tried to reclaim within a
* time window (quota_reset_interval_ms) and makes no more than this limit is
* tried. This can be used for limiting consumption of CPU and IO. If this
* value is zero, the limit is disabled.
*
* 128 MiB by default.
*/
static unsigned long quota_sz __read_mostly = 128 * 1024 * 1024;
module_param(quota_sz, ulong, 0600);
/*
* The time/size quota charge reset interval in milliseconds.
*
* The charge reset interval for the quota of time (quota_ms) and size
* (quota_sz). That is, DAMON_RECLAIM does not try reclamation for more than
* quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms
* milliseconds.
*
* 1 second by default.
*/
static unsigned long quota_reset_interval_ms __read_mostly = 1000;
module_param(quota_reset_interval_ms, ulong, 0600);
/*
* The watermarks check time interval in microseconds.
*
* Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is
* enabled but inactive due to its watermarks rule. 5 seconds by default.
*/
static unsigned long wmarks_interval __read_mostly = 5000000;
module_param(wmarks_interval, ulong, 0600);
/*
* Free memory rate (per thousand) for the high watermark.
*
* If free memory of the system in bytes per thousand bytes is higher than
* this, DAMON_RECLAIM becomes inactive, so it does nothing but periodically
* checks the watermarks. 500 (50%) by default.
*/
static unsigned long wmarks_high __read_mostly = 500;
module_param(wmarks_high, ulong, 0600);
/*
* Free memory rate (per thousand) for the middle watermark.
*
* If free memory of the system in bytes per thousand bytes is between this and
* the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring
* and the reclaiming. 400 (40%) by default.
*/
static unsigned long wmarks_mid __read_mostly = 400;
module_param(wmarks_mid, ulong, 0600);
/*
* Free memory rate (per thousand) for the low watermark.
*
* If free memory of the system in bytes per thousand bytes is lower than this,
* DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks
* the watermarks. In the case, the system falls back to the LRU-based page
* granularity reclamation logic. 200 (20%) by default.
*/
static unsigned long wmarks_low __read_mostly = 200;
module_param(wmarks_low, ulong, 0600);
/*
* Sampling interval for the monitoring in microseconds.
*
* The sampling interval of DAMON for the cold memory monitoring. Please refer
* to the DAMON documentation for more detail. 5 ms by default.
*/
static unsigned long sample_interval __read_mostly = 5000;
module_param(sample_interval, ulong, 0600);
/*
* Aggregation interval for the monitoring in microseconds.
*
* The aggregation interval of DAMON for the cold memory monitoring. Please
* refer to the DAMON documentation for more detail. 100 ms by default.
*/
static unsigned long aggr_interval __read_mostly = 100000;
module_param(aggr_interval, ulong, 0600);
/*
* Minimum number of monitoring regions.
*
* The minimal number of monitoring regions of DAMON for the cold memory
* monitoring. This can be used to set lower-bound of the monitoring quality.
* But, setting this too high could result in increased monitoring overhead.
* Please refer to the DAMON documentation for more detail. 10 by default.
*/
static unsigned long min_nr_regions __read_mostly = 10;
module_param(min_nr_regions, ulong, 0600);
/*
* Maximum number of monitoring regions.
*
* The maximum number of monitoring regions of DAMON for the cold memory
* monitoring. This can be used to set upper-bound of the monitoring overhead.
* However, setting this too low could result in bad monitoring quality.
* Please refer to the DAMON documentation for more detail. 1000 by default.
*/
static unsigned long max_nr_regions __read_mostly = 1000;
module_param(max_nr_regions, ulong, 0600);
/*
* Start of the target memory region in physical address.
*
* The start physical address of memory region that DAMON_RECLAIM will do work
* against. By default, biggest System RAM is used as the region.
*/
static unsigned long monitor_region_start __read_mostly;
module_param(monitor_region_start, ulong, 0600);
/*
* End of the target memory region in physical address.
*
* The end physical address of memory region that DAMON_RECLAIM will do work
* against. By default, biggest System RAM is used as the region.
*/
static unsigned long monitor_region_end __read_mostly;
module_param(monitor_region_end, ulong, 0600);
/*
* PID of the DAMON thread
*
* If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.
* Else, -1.
*/
static int kdamond_pid __read_mostly = -1;
module_param(kdamond_pid, int, 0400);
/*
* Number of memory regions that tried to be reclaimed.
*/
static unsigned long nr_reclaim_tried_regions __read_mostly;
module_param(nr_reclaim_tried_regions, ulong, 0400);
/*
* Total bytes of memory regions that tried to be reclaimed.
*/
static unsigned long bytes_reclaim_tried_regions __read_mostly;
module_param(bytes_reclaim_tried_regions, ulong, 0400);
/*
* Number of memory regions that successfully be reclaimed.
*/
static unsigned long nr_reclaimed_regions __read_mostly;
module_param(nr_reclaimed_regions, ulong, 0400);
/*
* Total bytes of memory regions that successfully be reclaimed.
*/
static unsigned long bytes_reclaimed_regions __read_mostly;
module_param(bytes_reclaimed_regions, ulong, 0400);
/*
* Number of times that the time/space quota limits have exceeded
*/
static unsigned long nr_quota_exceeds __read_mostly;
module_param(nr_quota_exceeds, ulong, 0400);
static struct damon_ctx *ctx;
static struct damon_target *target;
struct damon_reclaim_ram_walk_arg {
unsigned long start;
unsigned long end;
};
static int walk_system_ram(struct resource *res, void *arg)
{
struct damon_reclaim_ram_walk_arg *a = arg;
if (a->end - a->start < res->end - res->start) {
a->start = res->start;
a->end = res->end;
}
return 0;
}
/*
* Find biggest 'System RAM' resource and store its start and end address in
* @start and @end, respectively. If no System RAM is found, returns false.
*/
static bool get_monitoring_region(unsigned long *start, unsigned long *end)
{
struct damon_reclaim_ram_walk_arg arg = {};
walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
if (arg.end <= arg.start)
return false;
*start = arg.start;
*end = arg.end;
return true;
}
static struct damos *damon_reclaim_new_scheme(void)
{
struct damos_watermarks wmarks = {
.metric = DAMOS_WMARK_FREE_MEM_RATE,
.interval = wmarks_interval,
.high = wmarks_high,
.mid = wmarks_mid,
.low = wmarks_low,
};
struct damos_quota quota = {
/*
* Do not try reclamation for more than quota_ms milliseconds
* or quota_sz bytes within quota_reset_interval_ms.
*/
.ms = quota_ms,
.sz = quota_sz,
.reset_interval = quota_reset_interval_ms,
/* Within the quota, page out older regions first. */
.weight_sz = 0,
.weight_nr_accesses = 0,
.weight_age = 1
};
struct damos *scheme = damon_new_scheme(
/* Find regions having PAGE_SIZE or larger size */
PAGE_SIZE, ULONG_MAX,
/* and not accessed at all */
0, 0,
/* for min_age or more micro-seconds, and */
min_age / aggr_interval, UINT_MAX,
/* page out those, as soon as found */
DAMOS_PAGEOUT,
/* under the quota. */
"a,
/* (De)activate this according to the watermarks. */
&wmarks);
return scheme;
}
static int damon_reclaim_turn(bool on)
{
struct damon_region *region;
struct damos *scheme;
int err;
if (!on) {
err = damon_stop(&ctx, 1);
if (!err)
kdamond_pid = -1;
return err;
}
err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
min_nr_regions, max_nr_regions);
if (err)
return err;
if (monitor_region_start > monitor_region_end)
return -EINVAL;
if (!monitor_region_start && !monitor_region_end &&
!get_monitoring_region(&monitor_region_start,
&monitor_region_end))
return -EINVAL;
/* DAMON will free this on its own when finish monitoring */
region = damon_new_region(monitor_region_start, monitor_region_end);
if (!region)
return -ENOMEM;
damon_add_region(region, target);
/* Will be freed by 'damon_set_schemes()' below */
scheme = damon_reclaim_new_scheme();
if (!scheme) {
err = -ENOMEM;
goto free_region_out;
}
err = damon_set_schemes(ctx, &scheme, 1);
if (err)
goto free_scheme_out;
err = damon_start(&ctx, 1);
if (!err) {
kdamond_pid = ctx->kdamond->pid;
return 0;
}
free_scheme_out:
damon_destroy_scheme(scheme);
free_region_out:
damon_destroy_region(region, target);
return err;
}
#define ENABLE_CHECK_INTERVAL_MS 1000
static struct delayed_work damon_reclaim_timer;
static void damon_reclaim_timer_fn(struct work_struct *work)
{
static bool last_enabled;
bool now_enabled;
now_enabled = enabled;
if (last_enabled != now_enabled) {
if (!damon_reclaim_turn(now_enabled))
last_enabled = now_enabled;
else
enabled = last_enabled;
}
schedule_delayed_work(&damon_reclaim_timer,
msecs_to_jiffies(ENABLE_CHECK_INTERVAL_MS));
}
static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);
static int damon_reclaim_after_aggregation(struct damon_ctx *c)
{
struct damos *s;
/* update the stats parameter */
damon_for_each_scheme(s, c) {
nr_reclaim_tried_regions = s->stat.nr_tried;
bytes_reclaim_tried_regions = s->stat.sz_tried;
nr_reclaimed_regions = s->stat.nr_applied;
bytes_reclaimed_regions = s->stat.sz_applied;
nr_quota_exceeds = s->stat.qt_exceeds;
}
return 0;
}
static int __init damon_reclaim_init(void)
{
ctx = damon_new_ctx();
if (!ctx)
return -ENOMEM;
damon_pa_set_operations(ctx);
ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
target = damon_new_target();
if (!target) {
damon_destroy_ctx(ctx);
return -ENOMEM;
}
damon_add_target(ctx, target);
schedule_delayed_work(&damon_reclaim_timer, 0);
return 0;
}
module_init(damon_reclaim_init);
