blk-iolatency: only call ktime_get() if needed (6e2fa4dd) · Commits · 戴 / test

ktime_to_ns(ktime_get()), which is expensive, does not need to be called if blk_iolatency_enabled() return false in blkcg_iolatency_done_bio(). Postponing ktime_to_ns(ktime_get()) execution reduces the CPU usage when blk_iolatency is disabled. Signed-off-by:

Hongnan Li <hongnan.li@linux.alibaba.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-iolatency.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -591,7 +591,7 @@ static void blkcg_iolatency_done_bio(struct rq_qos rqos, struct bio bio)
		struct rq_wait *rqw;
		struct iolatency_grp *iolat;
		u64 window_start;
		u64 now = ktime_to_ns(ktime_get());
		u64 now;
		bool issue_as_root = bio_issue_as_root_blkg(bio);
		bool enabled = false;
		int inflight = 0;
		@@ -608,6 +608,7 @@ static void blkcg_iolatency_done_bio(struct rq_qos rqos, struct bio bio)
		if (!enabled)
		return;

		now = ktime_to_ns(ktime_get());
		while (blkg && blkg->parent) {
		iolat = blkg_to_lat(blkg);
		if (!iolat) {

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