Messages in this thread | | | Date | Mon, 16 Oct 2023 15:33:58 +0200 | Subject | Re: [PATCH] sched/eevdf: Toggle eligibility through sched_feat | From | Tor Vic <> |
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On 10/15/23 12:44, Peter Zijlstra wrote: > On Thu, Oct 12, 2023 at 10:02:13PM -0500, Youssef Esmat wrote: >> Interactive workloads see performance gains by disabling eligibility >> checks (EEVDF->EVDF). Disabling the checks reduces the number of >> context switches and delays less important work (higher deadlines/nice >> values) in favor of more important work (lower deadlines/nice values). >> >> That said, that can add large latencies for some work loads and as the >> default is eligibility on, but allowing it to be turned off when >> beneficial. >> >> Signed-off-by: Youssef Esmat <youssefesmat@chromium.org> >> Link: https://lore.kernel.org/lkml/CA+q576MS0-MV1Oy-eecvmYpvNT3tqxD8syzrpxQ-Zk310hvRbw@mail.gmail.com/ >> --- >> kernel/sched/fair.c | 3 +++ >> kernel/sched/features.h | 1 + >> 2 files changed, 4 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index a751e552f253..16106da5a354 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -728,6 +728,9 @@ int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se) >> s64 avg = cfs_rq->avg_vruntime; >> long load = cfs_rq->avg_load; >> >> + if (!sched_feat(ENFORCE_ELIGIBILITY)) >> + return 1; >> + >> if (curr && curr->on_rq) { >> unsigned long weight = scale_load_down(curr->load.weight); >> > > Right.. could you pretty please try: > > git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/eevdf > > as of yesterday or so. > > It defaults to (EEVDF relevant features): > > SCHED_FEAT(PLACE_LAG, true) > SCHED_FEAT(PLACE_DEADLINE_INITIAL, true) > SCHED_FEAT(PREEMPT_SHORT, true) > SCHED_FEAT(PLACE_SLEEPER, false) > SCHED_FEAT(GENTLE_SLEEPER, true) > SCHED_FEAT(EVDF, false) > SCHED_FEAT(DELAY_DEQUEUE, true) > SCHED_FEAT(GENTLE_DELAY, true) > > If that doesn't do well enough, could you please try, in order of > preference: > > 2) NO_GENTLE_DELAY > 3) NO_DELAY_DEQUEUE, PLACE_SLEEPER > 4) NO_DELAY_DEQUEUE, PLACE_SLEEPER, NO_GENTLE_SLEEPER
I'm very interested in this scheduler stuff, but I know nothing about the code.
Still, I ran some very quick benchmarks on a dual-core Skylake laptop running 6.6-rc6. Base slice is 5 ms.
1) Without the recent patches from Peter's tree 2) With patches, default features 3) With patches, NO_GENTLE_DELAY 4) With patches, NO_DELAY_DEQUEUE + PLACE_SLEEPER 5) With patches, like 4) + NO_GENTLE_SLEEPER 6) With patches, like 5) + EVDF
$ perf stat -r 7 -e cs,migrations,cache-misses,branch-misses -- perf bench sched messaging -g 20 -l 1000 -p
test | seconds | cs | migrations | cache miss | branch miss | ------|---------|------|------------|------------|-------------| 1) | 2,90 | 192K | 6,7K | 99M | 60M | 2) | 2,97 | 226K | 6,9K | 102M | 61M | 3) | 3,00 | 247K | 6,9K | 108M | 62M | 4) | 2,92 | 182K | 7,2K | 101M | 60M | 5) | 2,94 | 203K | 6,8K | 101M | 60M | 6) | 2,79 | 84K | 6,4K | 94M | 57M |
$ stress-ng --bsearch 2 --matrix 2 --matrix-method prod --timeout 30 --metrics-brief [results in bogo ops/s]
test | bsearch | matrix | ------|---------|--------| 1) | 392 | 588 | 2) | 512 | 688 | 3) | 512 | 663 | 4) | 512 | 688 | 5) | 511 | 686 | 6) | 510 | 655 |
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I don't know if this info is useful enough for you scheduler people, but I hope it helps.
Cheers, Tor
> > I really don't like the EVDF option, and I think you'll end up > regretting using it sooner rather than later, just to make this one > benchmark you have happy. > > I'm hoping the default is enough, but otherwise any of the above should > be a *much* better scheduler. > > Also, bonus points if you can create us a stand alone benchmark that > captures your metric (al-la facebook's schbench) without the whole > chrome nonsense, that'd be epic. >
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