Messages in this thread | | | From | Josh Don <> | Date | Wed, 29 Mar 2023 11:54:58 -0700 | Subject | Re: [PATCH 08/17] sched/fair: Implement an EEVDF like policy |
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On Wed, Mar 29, 2023 at 1:12 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, Mar 28, 2023 at 06:26:51PM -0700, Josh Don wrote: > > > > @@ -5088,19 +5307,20 @@ dequeue_entity(struct cfs_rq *cfs_rq, st > > > static void > > > check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > > { > > > - unsigned long ideal_runtime, delta_exec; > > > + unsigned long delta_exec; > > > struct sched_entity *se; > > > s64 delta; > > > > > > - /* > > > - * When many tasks blow up the sched_period; it is possible that > > > - * sched_slice() reports unusually large results (when many tasks are > > > - * very light for example). Therefore impose a maximum. > > > - */ > > > - ideal_runtime = min_t(u64, sched_slice(cfs_rq, curr), sysctl_sched_latency); > > > + if (sched_feat(EEVDF)) { > > > + if (pick_eevdf(cfs_rq) != curr) > > > + goto preempt; > > > > This could shortcircuit the loop in pick_eevdf once we find a best > > that has less vruntime and sooner deadline than curr, since we know > > we'll never pick curr in that case. Might help performance when we > > have a large tree for this cfs_rq. > > Yeah, one of the things I did consider was having this set cfs_rq->next > such that the reschedule pick doesn't have to do the pick again. But I > figured keep things simple for now.
Yea that makes sense. I was thinking something similar along the lines of cfs_rq->next as another way to avoid duplicate computation. But agreed this can be a future optimization.
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