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| author | Dmitry Monakhov <dmonakhov@gmail.com> | 2019-11-01 13:11:10 +0000 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-11-20 16:10:29 -0700 |
| commit | 40d47c155e8ae9bcb3f2d0d01cf14d903c664726 (patch) | |
| tree | 80e724192c2ecdb7b0f7199ecadc452fa17d48c8 | |
| parent | c6da429ea988de8f9330405fc405ee32479b5bd5 (diff) | |
| download | linux-40d47c155e8ae9bcb3f2d0d01cf14d903c664726.tar.gz | |
block,bfq: Skip tracing hooks if possible
In most cases blk_tracing is not active, but bfq_log_bfqq macro
generate pid_str unconditionally, which result in significant overhead.
## Test
modprobe null_blk
echo bfq > /sys/block/nullb0/queue/scheduler
fio --name=t --ioengine=libaio --direct=1 --filename=/dev/nullb0 \
--runtime=30 --time_based=1 --rw=write --iodepth=128 --bs=4k
# Results
| | baseline | w/ patch | gain |
| iops | 113.19K | 126.42K | +11% |
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/bfq-iosched.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 9c82c1f35716..8526f20c53bc 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -1068,6 +1068,8 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq); #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \ char pid_str[MAX_PID_STR_LENGTH]; \ + if (likely(!blk_trace_note_message_enabled((bfqd)->queue))) \ + break; \ bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH); \ blk_add_cgroup_trace_msg((bfqd)->queue, \ bfqg_to_blkg(bfqq_group(bfqq))->blkcg, \ @@ -1084,6 +1086,8 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq); #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \ char pid_str[MAX_PID_STR_LENGTH]; \ + if (likely(!blk_trace_note_message_enabled((bfqd)->queue))) \ + break; \ bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH); \ blk_add_trace_msg((bfqd)->queue, "bfq%s%c " fmt, pid_str, \ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \ |