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authorLuca Miccio <lucmiccio@gmail.com>2017-11-13 07:34:10 +0100
committerJens Axboe <axboe@kernel.dk>2017-11-14 20:13:33 -0700
commita33801e8b4735b8d473f963e5854172f9cde3e8b (patch)
treeacebf1dbfbe5effb178f76d31b841b9fb24f45fd /block/bfq-iosched.c
parent24bfd19bb7890255693ee5cb6dc100d8d215d00b (diff)
downloadlinux-0-day-a33801e8b4735b8d473f963e5854172f9cde3e8b.tar.gz
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.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 69e05f8..bcb6d21 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;
/*