Messages in this thread Patch in this message | | | From | Chengming Zhou <> | Subject | [PATCH] sched/core: Minor optimize ttwu_runnable() | Date | Wed, 2 Nov 2022 18:23:43 +0800 |
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ttwu_runnable() is used as a fast wakeup path when the wakee task is between set_current_state() and schedule(), in which case all we need to do is change p->state back to TASK_RUNNING. So we don't need to update_rq_clock() and check_preempt_curr() in this case.
Some performance numbers using mmtests/perfpipe on Intel Xeon server:
linux-next patched Min Time 8.67 ( 0.00%) 8.66 ( 0.13%) 1st-qrtle Time 8.83 ( 0.00%) 8.72 ( 1.19%) 2nd-qrtle Time 8.90 ( 0.00%) 8.76 ( 1.57%) 3rd-qrtle Time 8.98 ( 0.00%) 8.82 ( 1.82%) Max-1 Time 8.67 ( 0.00%) 8.66 ( 0.13%) Max-5 Time 8.67 ( 0.00%) 8.66 ( 0.13%) Max-10 Time 8.79 ( 0.00%) 8.69 ( 1.09%) Max-90 Time 9.01 ( 0.00%) 8.84 ( 1.94%) Max-95 Time 9.02 ( 0.00%) 8.85 ( 1.86%) Max-99 Time 9.02 ( 0.00%) 8.88 ( 1.56%) Max Time 9.59 ( 0.00%) 8.89 ( 7.29%) Amean Time 8.92 ( 0.00%) 8.77 * 1.65%*
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> --- kernel/sched/core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 87c9cdf37a26..3785418de127 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3718,9 +3718,8 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags) rq = __task_rq_lock(p, &rf); if (task_on_rq_queued(p)) { - /* check_preempt_curr() may use rq clock */ - update_rq_clock(rq); - ttwu_do_wakeup(rq, p, wake_flags, &rf); + WRITE_ONCE(p->__state, TASK_RUNNING); + trace_sched_wakeup(p); ret = 1; } __task_rq_unlock(rq, &rf); -- 2.37.2
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