Messages in this thread | | | Date | Tue, 8 Dec 2020 10:59:00 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU |
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On Tue, Dec 08, 2020 at 11:07:19AM +0100, Dietmar Eggemann wrote: > On 07/12/2020 10:15, Mel Gorman wrote: > > SIS_AVG_CPU was introduced as a means of avoiding a search when the > > average search cost indicated that the search would likely fail. It > > was a blunt instrument and disabled by 4c77b18cf8b7 ("sched/fair: Make > > select_idle_cpu() more aggressive") and later replaced with a proportional > > search depth by 1ad3aaf3fcd2 ("sched/core: Implement new approach to > > scale select_idle_cpu()"). > > > > While there are corner cases where SIS_AVG_CPU is better, it has now been > > disabled for almost three years. As the intent of SIS_PROP is to reduce > > the time complexity of select_idle_cpu(), lets drop SIS_AVG_CPU and focus > > on SIS_PROP as a throttling mechanism. > > > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > --- > > kernel/sched/fair.c | 3 --- > > kernel/sched/features.h | 1 - > > 2 files changed, 4 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 98075f9ea9a8..23934dbac635 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -6161,9 +6161,6 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > > avg_idle = this_rq()->avg_idle / 512; > > avg_cost = this_sd->avg_scan_cost + 1; > > > > - if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) > > - return -1; > > - > > if (sched_feat(SIS_PROP)) { > > u64 span_avg = sd->span_weight * avg_idle; > > if (span_avg > 4*avg_cost) > > Nitpick: > > Since now avg_cost and avg_idle are only used w/ SIS_PROP, they could go > completely into the SIS_PROP if condition. >
Yeah, I can do that. In the initial prototype, that happened in a separate patch that split out SIS_PROP into a helper function and I never merged it back. It's a trivial change.
Thanks.
-- Mel Gorman SUSE Labs
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