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>
1 file changed