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.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'block/bfq-iosched.h') diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index ac0809c72c98..91c4390903a1 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -689,7 +689,7 @@ enum bfqq_expiration { }; struct bfqg_stats { -#ifdef CONFIG_BFQ_GROUP_IOSCHED +#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) /* number of ios merged */ struct blkg_rwstat merged; /* total time spent on device in ns, may not be accurate w/ queueing */ @@ -717,7 +717,7 @@ struct bfqg_stats { uint64_t start_idle_time; uint64_t start_empty_time; uint16_t flags; -#endif /* CONFIG_BFQ_GROUP_IOSCHED */ +#endif /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */ }; #ifdef CONFIG_BFQ_GROUP_IOSCHED -- cgit v1.2.3