On 01/07/2020 08:05, Hongnan Li wrote:
> ktime_to_ns(ktime_get()) which is expensive do not need to be executed if
> blk_iolatency_enabled() return false in blkcg_iolatency_done_bio().
> Postponing ktime_to_ns(ktime_get()) execution can reduce CPU usage
> when blk_iolatency was disabled.
>
> Signed-off-by: Hongnan Li <hongnan.li@xxxxxxxxxxxxxxxxx>
> ---
> block/blk-iolatency.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
> index c128d50..8c1487e 100644
> --- a/block/blk-iolatency.c
> +++ b/block/blk-iolatency.c
> @@ -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());
> +
> 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;
>
> + u64 now = ktime_to_ns(ktime_get());
> while (blkg && blkg->parent) {
> iolat = blkg_to_lat(blkg);
> if (!iolat) {
>
You're mixing declarations and code.
please do
- u64 now = ktime_to_ns(ktime_get());
+ u64 now;
[...]
+ now = ktime_to_ns(ktime_get());
