Messages in this thread | | | Date | Sat, 15 Oct 2022 17:43:12 +0800 | Subject | Re: [PATCH v2] sched/psi: Fix avgs_work re-arm in psi_avgs_work() | From | Chengming Zhou <> |
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On 2022/10/15 00:41, Suren Baghdasaryan wrote: > On Fri, Oct 14, 2022 at 7:18 AM Johannes Weiner <hannes@cmpxchg.org> wrote: >> >> On Fri, Oct 14, 2022 at 07:05:51PM +0800, Chengming Zhou wrote: >>> Pavan reported a problem that PSI avgs_work idle shutoff is not >>> working at all. Because PSI_NONIDLE condition would be observed in >>> psi_avgs_work()->collect_percpu_times()->get_recent_times() even if >>> only the kworker running avgs_work on the CPU. >>> >>> Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off") >>> avoided the ping-pong wake problem when the worker sleep, psi_avgs_work() >>> still will always re-arm the avgs_work, so shutoff is not working. >>> >>> This patch changes to use PSI_STATE_RESCHEDULE to flag whether to >>> re-arm avgs_work in get_recent_times(). For the current CPU, we re-arm >>> avgs_work only when (NR_RUNNING > 1 || NR_IOWAIT > 0 || NR_MEMSTALL > 0), >>> for other CPUs we can just check PSI_NONIDLE delta. The new flag >>> is only used in psi_avgs_work(), so we check in get_recent_times() >>> that current_work() is avgs_work. >>> >>> One potential problem is that the brief period of non-idle time >>> incurred between the aggregation run and the kworker's dequeue will >>> be stranded in the per-cpu buckets until avgs_work run next time. >>> The buckets can hold 4s worth of time, and future activity will wake >>> the avgs_work with a 2s delay, giving us 2s worth of data we can leave >>> behind when shut off the avgs_work. If the kworker run other works after >>> avgs_work shut off and doesn't have any scheduler activities for 2s, >>> this maybe a problem. >>> >>> Reported-by: Pavan Kondeti <quic_pkondeti@quicinc.com> >>> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> >> >> Acked-by: Johannes Weiner <hannes@cmpxchg.org> > > Please make sure to test the final version. With that done, > > Acked-by: Suren Baghdasaryan <surenb@google.com>
Thanks! Yes, I did test with this version on VM yesterday, so add:
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
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