linux-kernel - Re: [tip: sched/core] sched/eevdf: Curb wakeup-preemption

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Message-ID: <02f6a15f094adb3c8d9957b031941d6bd10c2e43.camel@gmx.de>
Date:   Mon, 21 Aug 2023 17:30:58 +0200
From:   Mike Galbraith <efault@....de>
To:     K Prateek Nayak <kprateek.nayak@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        x86@...nel.org, Chen Yu <yu.c.chen@...el.com>,
        Gautham Shenoy <gautham.shenoy@....com>
Subject: Re: [tip: sched/core] sched/eevdf: Curb wakeup-preemption

On Mon, 2023-08-21 at 16:09 +0530, K Prateek Nayak wrote:
> Hello Peter,
>
> Sorry for being late to the party but couple of benchmarks are unhappy
> (very!) with eevdf, even with this optimization. I'll leave the results
> of testing on a dual socket 3rd Generation EPYC System (2 x 64C/128T)
> running in NPS1 mode below.
>
> tl;dr
>
> - Hackbench with medium load, tbench when overloaded, and DeathStarBench
>   are not a fan of EEVDF so far :(

FWIW, there are more tbench shards lying behind EEVDF than in front.

tbench 8 on old i7-4790 box
4.4.302      4024
6.4.11       3668
6.4.11-eevdf 3522

I went a-hunting once, but it didn't go well.  There were a couple
identifiable sched related dips/recoveries, but the overall result was
a useless downward trending mess.

	-Mike