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| author | Luca Miccio <lucmiccio@gmail.com> | 2017-11-13 09:34:10 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-11-15 06:13:33 +0300 |
| commit | a33801e8b4735b8d473f963e5854172f9cde3e8b (patch) | |
| tree | acebf1dbfbe5effb178f76d31b841b9fb24f45fd /block/bfq-iosched.h | |
| parent | 24bfd19bb7890255693ee5cb6dc100d8d215d00b (diff) | |
| download | linux-a33801e8b4735b8d473f963e5854172f9cde3e8b.tar.xz | |
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.h')
| -rw-r--r-- | block/bfq-iosched.h | 4 |
1 files changed, 2 insertions, 2 deletions
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 |