The following commit has been merged into the sched/core branch of tip: Commit-ID: d7d607096ae6d378b4e92d49946d22739c047d4c Gitweb: https://git.kernel.org/tip/d7d607096ae6d378b4e92d49946d22739c047d4c Author: Vincent Donnefort <vincent.donnefort@xxxxxxx> AuthorDate: Mon, 21 Jun 2021 11:37:52 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 22 Jun 2021 16:41:59 +02:00 sched/rt: Fix Deadline utilization tracking during policy change DL keeps track of the utilization on a per-rq basis with the structure avg_dl. This utilization is updated during task_tick_dl(), put_prev_task_dl() and set_next_task_dl(). However, when the current running task changes its policy, set_next_task_dl() which would usually take care of updating the utilization when the rq starts running DL tasks, will not see a such change, leaving the avg_dl structure outdated. When that very same task will be dequeued later, put_prev_task_dl() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the DL utilization signal. The signal would eventually recover from this issue after few ms. Even if no DL tasks are run, avg_dl is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_dl, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to DL. Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking") Signed-off-by: Vincent Donnefort <vincent.donnefort@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@xxxxxxx --- kernel/sched/deadline.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 22878cd..aaacd6c 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2497,6 +2497,8 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) check_preempt_curr_dl(rq, p, 0); else resched_curr(rq); + } else { + update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0); } }
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