Messages in this thread | | | Date | Sat, 26 Aug 2023 21:46:59 +0100 | From | Qais Yousef <> | Subject | Re: [RFC PATCH] sched/fair: update the vruntime to be max vruntime when yield |
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On 08/23/23 10:03, Xuewen Yan wrote: > Hi Vincent > > Thanks for your patience to reply! > > On Tue, Aug 22, 2023 at 11:55 PM Vincent Guittot > <vincent.guittot@linaro.org> wrote: > > > > On Mon, 21 Aug 2023 at 09:51, Xuewen Yan <xuewen.yan94@gmail.com> wrote: > > > > > > Hi Vincent > > > > > > I have some questions to ask,and hope you can help. > > > > > > For this problem, In our platform, We found that the vruntime of some > > > tasks will become abnormal over time, resulting in tasks with abnormal > > > vruntime not being scheduled. > > > The following are some tasks in runqueue: > > > [status: curr] pid: 25501 prio: 116 vrun: 16426426403395799812 > > > [status: skip] pid: 25496 prio: 116 vrun: 16426426403395800756 > > > exec_start: 326203047009312 sum_ex: 29110005599 > > > [status: pend] pid: 25497 prio: 116 vrun: 16426426403395800705 > > > exec_start: 326203047002235 sum_ex: 29110508751 > > > [status: pend] pid: 25321 prio: 130 vrun: 16668783152248554223 > > > exec_start: 0 sum_ex: 16198728 > > > [status: pend] pid: 25798 prio: 112 vrun: 17467381818375696015 > > > exec_start: 0 sum_ex: 9574265 > > > [status: pend] pid: 22282 prio: 120 vrun: 18010356387391134435 > > > exec_start: 0 sum_ex: 53192 > > > [status: pend] pid: 24259 prio: 120 vrun: 359915144918430571 > > > exec_start: 0 sum_ex: 20508197 > > > [status: pend] pid: 25988 prio: 120 vrun: 558552749871164416 > > > exec_start: 0 sum_ex: 2099153 > > > [status: pend] pid: 21857 prio: 124 vrun: 596088822758688878 > > > exec_start: 0 sum_ex: 246057024 > > > [status: pend] pid: 26614 prio: 130 vrun: 688210016831095807 > > > exec_start: 0 sum_ex: 968307 > > > [status: pend] pid: 14229 prio: 120 vrun: 816756964596474655 > > > exec_start: 0 sum_ex: 793001 > > > [status: pend] pid: 23866 prio: 120 vrun: 1313723379399791578 > > > exec_start: 0 sum_ex: 1507038 > > > ... > > > [status: pend] pid: 25970 prio: 120 vrun: 6830180148220001175 > > > exec_start: 0 sum_ex: 2531884 > > > [status: pend] pid: 25965 prio: 120 vrun: 6830180150700833203 > > > exec_start: 0 sum_ex: 8031809 > > > > > > And According to your suggestion, we test the patch: > > > https://lore.kernel.org/all/20230130122216.3555094-1-rkagan@amazon.de/T/#u > > > The above exception is gone. > > > > > > But when we tested using patch: > > > https://lore.kernel.org/all/20230130122216.3555094-1-rkagan@amazon.de/T/#u > > > and > > > https://lore.kernel.org/all/20230317160810.107988-1-vincent.guittot@linaro.org/ > > > Unfortunately, our issue occurred again. > > > > > > So we have to use a workaround solution to our problem, that is to > > > change the sleeping time's judgement to 60s. > > > + > > > + sleep_time -= se->exec_start; > > > + if (sleep_time > ((1ULL << 63) / scale_load_down(NICE_0_LOAD))) > > > + return true; > > > > > > to > > > > > > + sleep_time -= se->exec_start; > > > +if ((s64)sleep_time > 60LL * NSEC_PER_SEC) > > > + return true; > > > > > > At this time, the issue also did not occur again. > > > > > > But this modification doesn't actually solve the real problem. And then > > > > yes, it resetx the task's vruntime once the delta go above 60sec but > > your problem is still there > > > > > Qais suggested us to try this patch: > > > https://lore.kernel.org/all/20190709115759.10451-1-chris.redpath@arm.com/T/#u > > > > we have the below in v6.0 to fix the problem of stalled clock update > > instead of the above > > commit e2f3e35f1f5a ("sched/fair: Decay task PELT values during wakeup > > migration") > > > > Which kernel version are you using ? > > We test in kernel5.4, and kernel5.15 also seems to have this problem. > > And I will later test the commit e2f3e35f1f5a ("sched/fair: Decay > task PELT values during wakeup migration").
I think it might be worth to cherry-pick the first two patches of that series to 5.10 and 5.15 (5.4 is a bit too old for me at least to work with).
Although they've been rare enough, but the util swing problem does pop up every once in a while. And if it helps with this vruntime it might be a simple thing to do to cherry pick these two patches after all. I think they'll apply without a problem - I'll look at this.
Cheers
-- Qais Yousef
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