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| author | Luca Miccio <lucmiccio@gmail.com> | 2017-11-13 07:34:10 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-11-14 20:13:33 -0700 |
| commit | a33801e8b4735b8d473f963e5854172f9cde3e8b (patch) | |
| tree | acebf1dbfbe5effb178f76d31b841b9fb24f45fd /block/bfq-iosched.c | |
| parent | 24bfd19bb7890255693ee5cb6dc100d8d215d00b (diff) | |
| download | lwn-a33801e8b4735b8d473f963e5854172f9cde3e8b.tar.gz lwn-a33801e8b4735b8d473f963e5854172f9cde3e8b.zip | |
block, bfq: move debug blkio stats behind CONFIG_DEBUG_BLK_CGROUP
BFQ currently creates, and updates, its own instance of the whole
set of blkio statistics that cfq creates. Yet, from the comments
of Tejun Heo in [1], it turned out that most of these statistics
are meant/useful only for debugging. This commit makes BFQ create
the latter, debugging statistics only if the option
CONFIG_DEBUG_BLK_CGROUP is set.
By doing so, this commit also enables BFQ to enjoy a high perfomance
boost. The reason is that, if CONFIG_DEBUG_BLK_CGROUP is not set, then
BFQ has to update far fewer statistics, and, in particular, not the
heaviest to update. To give an idea of the benefits, if
CONFIG_DEBUG_BLK_CGROUP is not set, then, on an Intel i7-4850HQ, and
with 8 threads doing random I/O in parallel on null_blk (configured
with 0 latency), the throughput of BFQ grows from 310 to 400 KIOPS
(+30%). We have measured similar or even much higher boosts with other
CPUs: e.g., +45% with an ARM CortexTM-A53 Octa-core. Our results have
been obtained and can be reproduced very easily with the script in [1].
[1] https://www.spinics.net/lists/linux-block/msg18943.html
Suggested-by: Tejun Heo <tj@kernel.org>
Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Lee Tibbert <lee.tibbert@gmail.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Luca Miccio <lucmiccio@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 69e05f861daf..bcb6d21baf12 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3693,14 +3693,14 @@ static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; struct request *rq; -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) struct bfq_queue *in_serv_queue, *bfqq; bool waiting_rq, idle_timer_disabled; #endif spin_lock_irq(&bfqd->lock); -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) in_serv_queue = bfqd->in_service_queue; waiting_rq = in_serv_queue && bfq_bfqq_wait_request(in_serv_queue); @@ -3714,7 +3714,7 @@ static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) #endif spin_unlock_irq(&bfqd->lock); -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) bfqq = rq ? RQ_BFQQ(rq) : NULL; if (!idle_timer_disabled && !bfqq) return rq; @@ -4281,7 +4281,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, { struct request_queue *q = hctx->queue; struct bfq_data *bfqd = q->elevator->elevator_data; -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) struct bfq_queue *bfqq = RQ_BFQQ(rq); bool idle_timer_disabled = false; unsigned int cmd_flags; @@ -4304,7 +4304,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, else list_add_tail(&rq->queuelist, &bfqd->dispatch); } else { -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) idle_timer_disabled = __bfq_insert_request(bfqd, rq); /* * Update bfqq, because, if a queue merge has occurred @@ -4323,7 +4323,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, } } -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) /* * Cache cmd_flags before releasing scheduler lock, because rq * may disappear afterwards (for example, because of a request @@ -4333,7 +4333,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, #endif spin_unlock_irq(&bfqd->lock); -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) if (!bfqq) return; /* |