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From: Wanpeng Li <kernellwp@gmail.com>
Date: Mon, 10 Oct 2016 18:09:14 +0800
Message-ID: <CANRm+CxGHVoJO6i1Yjcqk_njTgPiZKK2_EJ3f8nsKN92is0dsQ@mail.gmail.com>
Subject: Re: [PATCH] sched/fair: Do not decay new task load on first enqueue
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Yuyang Du <yuyang.du@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>
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2016-10-10 18:01 GMT+08:00 Matt Fleming <matt@codeblueprint.co.uk>:
> On Sun, 09 Oct, at 11:39:27AM, Wanpeng Li wrote:
>>
>> The difference between this patch and Peterz's is your patch have a
>> delta since activate_task()->enqueue_task() does do update_rq_clock(),
>> so why don't have the delta will cause low cpu machines (4 or 8) to
>> regress against your another reply in this thread?
>
> Both my patch and Peter's patch cause issues with low cpu machines. In
> <20161004201105.GP16071@codeblueprint.co.uk> I said,
>
>  "This patch causes some low cpu machines (4 or 8) to regress. It turns
>   out they regress with my patch too."
>
> Have I misunderstood your question?

I compare this one https://marc.info/?l=linux-kernel&m=147446511924571
with Peterz's patch.

>
> I ran out of time to investigate this last week, though I did try all
> proposed patches, including Vincent's, and none of them produced wins
> across the board.
>
> I should get a bit further this week.
>
> Vincent, Dietmar, did you guys ever get around to submitting your PELT
> tracepoint patches? Getting some introspection into the scheduler's
> load balancing decisions would speed up this sort of research.