linux-kernel - Re: [tip:sched/eevdf] [sched/fair] e0c2ff903c: phoronix-test-suite.blogbench.Write.final

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Message-ID: <20230815235201.GH971582@hirez.programming.kicks-ass.net>
Date:   Wed, 16 Aug 2023 01:52:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mike Galbraith <umgwanakikbuti@...il.com>
Cc:     Chen Yu <yu.c.chen@...el.com>,
        kernel test robot <oliver.sang@...el.com>,
        oe-lkp@...ts.linux.dev, lkp@...el.com,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [tip:sched/eevdf] [sched/fair]  e0c2ff903c:
 phoronix-test-suite.blogbench.Write.final_score -34.8% regression

On Mon, Aug 14, 2023 at 08:32:55PM +0200, Mike Galbraith wrote:

> I don't have that phoronix thingy, but the above didn't seem to do
> anything for hackbench here.

Yeah, looking at it this is because the lag and the request/slice are on
the same order of things.

More thinking required, but perhaps not at 2am.

> I whack eevdf with the stick below to dampen its scheduling enthusiasm
> a little, and it did help the hackbench deficit some.

I'm thinking there's an argument to be had the current WAKEUP_PREEMPTION
knob is at the wrong place and should be more or less where you put the
triddle at.