From a33801e8b4735b8d473f963e5854172f9cde3e8b Mon Sep 17 00:00:00 2001 From: Luca Miccio Date: Mon, 13 Nov 2017 07:34:10 +0100 Subject: 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 Suggested-by: Ulf Hansson Tested-by: Lee Tibbert Tested-by: Oleksandr Natalenko Signed-off-by: Luca Miccio Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-iosched.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'block/bfq-iosched.c') 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; /* -- cgit v1.2.3-59-g8ed1b