Messages in this thread | | | Date | Fri, 8 May 2020 21:01:18 +0800 | From | Peng Liu <> | Subject | Re: [PATCH] sched/fair: Fix nohz.next_balance update |
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On Tue, May 05, 2020 at 04:27:11PM +0200, Vincent Guittot wrote: > Le mardi 05 mai 2020 à 21:40:56 (+0800), Peng Liu a écrit : >
[...]
> > Your proposal below looks quite complex. IMO, one solution would be to move the > update of nohz.next_balance before calling rebalance_domains(this_rq, CPU_IDLE) > so you are back to the previous behavior. > > The only difference is that in case of an break because of need_resched, it > doesn't update nohz.next_balance. But on the other hand, we haven't yet > finished run rebalance_domains for all CPUs and some load_balance are still > pending. In fact, this will be done during next tick by an idle CPU. > > So I would be in favor of something as simple as : >
Vincent, could you refine this patch with some changelog? And have my reported-by if possible.
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 04098d678f3b..e028bc1c4744 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -10457,6 +10457,14 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, > } > } > > + /* > + * next_balance will be updated only when there is a need. > + * When the CPU is attached to null domain for ex, it will not be > + * updated. > + */ > + if (likely(update_next_balance)) > + nohz.next_balance = next_balance; > + > /* Newly idle CPU doesn't need an update */ > if (idle != CPU_NEWLY_IDLE) { > update_blocked_averages(this_cpu); > @@ -10477,14 +10485,6 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, > if (has_blocked_load) > WRITE_ONCE(nohz.has_blocked, 1); > > - /* > - * next_balance will be updated only when there is a need. > - * When the CPU is attached to null domain for ex, it will not be > - * updated. > - */ > - if (likely(update_next_balance)) > - nohz.next_balance = next_balance; > - > return ret; > } >
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