From: Peter Zijlstra <peterz@infradead.org>
To: Chris Mason <clm@meta.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
dietmar.eggemann@arm.com, vschneid@redhat.com
Subject: Re: scheduler performance regression since v6.11
Date: Tue, 13 May 2025 09:15:51 +0200 [thread overview]
Message-ID: <20250513071551.GC25763@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <d3c8527f-ffaf-4463-a305-17ca21a06ce8@meta.com>
On Mon, May 12, 2025 at 06:35:24PM -0400, Chris Mason wrote:
> If I take 54a58a787791 or 54a58a787791 and turn off the
> DELAY_DEQUEUE/ZERO features at run time, I don't get the performance
> back. But, if I patch them such that DELAY_DEQUEUE/ZERO default off
>
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index 7fdeb5576188c..94409e9831e97 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -37,8 +37,8 @@ SCHED_FEAT(CACHE_HOT_BUDDY, true)
> *
> * DELAY_ZERO clips the lag on dequeue (or wakeup) to 0.
> */
> -SCHED_FEAT(DELAY_DEQUEUE, true)
> -SCHED_FEAT(DELAY_ZERO, true)
> +SCHED_FEAT(DELAY_DEQUEUE, false)
> +SCHED_FEAT(DELAY_ZERO, false)
>
> It runs at 2M QPS again. If I enable DELAY_QUEUE/ZERO, I go back to 1.95M
Well, that's odd... there should not be residual effects like that. I'll
see if I can spot anything.
next prev parent reply other threads:[~2025-05-13 7:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-07 23:13 scheduler performance regression since v6.11 Chris Mason
2025-05-09 19:49 ` Peter Zijlstra
2025-05-12 18:08 ` Peter Zijlstra
2025-05-12 19:39 ` Chris Mason
2025-05-12 22:35 ` Chris Mason
2025-05-13 7:15 ` Peter Zijlstra [this message]
2025-05-16 10:18 ` Peter Zijlstra
2025-05-20 14:38 ` Dietmar Eggemann
2025-05-20 14:53 ` Chris Mason
2025-05-21 13:59 ` Dietmar Eggemann
2025-05-21 14:32 ` Chris Mason
2025-05-20 19:38 ` Peter Zijlstra
2025-05-21 14:02 ` Dietmar Eggemann
2025-05-21 15:02 ` Peter Zijlstra
2025-05-21 19:00 ` Peter Zijlstra
2025-05-21 14:54 ` Peter Zijlstra
2025-05-22 8:48 ` Peter Zijlstra
2025-05-22 15:00 ` Johannes Weiner
2025-05-23 15:40 ` Peter Zijlstra
2025-05-23 12:27 ` Dietmar Eggemann
2025-07-10 12:46 ` [tip: sched/core] sched/psi: Optimize psi_group_change() cpu_clock() usage tip-bot2 for Peter Zijlstra
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