Messages in this thread Patch in this message | | | Date | Mon, 12 Feb 2018 18:29:26 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/4] sched/fair: Do not migrate on wake_affine_weight if weights are equal |
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On Mon, Feb 12, 2018 at 02:58:56PM +0000, Mel Gorman wrote: > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c1091cb023c4..28c8d9c91955 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5747,7 +5747,16 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p, > prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2; > prev_eff_load *= capacity_of(this_cpu); > > - return this_eff_load <= prev_eff_load ? this_cpu : nr_cpumask_bits; > + /* > + * If sync, adjust the weight of prev_eff_load such that if > + * prev_eff == this_eff that select_idle_sibling will consider > + * stacking the wakee on top of the waker if no other CPU is > + * idle. > + */ > + if (sync) > + prev_eff_load += 1;
So where we had <= and would consistently favour pulling the task to the waking CPU when all else what equal, you now switch to <, such that when things are equal we do not pull.
That makes sense I suppose.
Except for sync wakeups, where you say, if everything else is equal, pull, which also makes sense, because sync says 'current' promises to go away.
OK.
> + > + return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits; > } > > static int wake_affine(struct sched_domain *sd, struct task_struct *p, > -- > 2.15.1 >
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