block,bfq: Skip tracing hooks if possible (40d47c15) · Commits · 戴 / test

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>

block/bfq-iosched.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -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', \

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