Messages in this thread | | | Subject | Re: [PATCH] block,bfq: Skip tracing hooks if possible | From | Paolo Valente <> | Date | Fri, 15 Nov 2019 07:47:43 +0100 |
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> Il giorno 1 nov 2019, alle ore 14:11, Dmitry Monakhov <dmonakhov@gmail.com> ha scritto: > > 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% | >
Thank you very much for this simple yet effective improvement.
Acked-by: Paolo Valente <paolo.valente@linaro.org>
> 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 >
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