From: Dmitry Monakhov <dmonakhov@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: axboe@kernel.dk, paolo.valente@linaro.org,
Dmitry Monakhov <dmonakhov@gmail.com>
Subject: [PATCH] block,bfq: Skip tracing hooks if possible
Date: Fri, 1 Nov 2019 13:11:10 +0000 [thread overview]
Message-ID: <20191101131110.18356-1-dmonakhov@gmail.com> (raw)
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% |
Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
---
block/bfq-iosched.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 5d1a519..b320fe9 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1062,6 +1062,8 @@ 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, \
@@ -1078,6 +1080,8 @@ 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', \
--
2.7.4
next reply other threads:[~2019-11-01 13:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-01 13:11 Dmitry Monakhov [this message]
2019-11-15 6:47 ` [PATCH] block,bfq: Skip tracing hooks if possible Paolo Valente
2019-11-20 23:11 ` Jens Axboe
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