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Message-ID: <139acc54-d24c-5437-7a9d-fa2438fffba4@joelfernandes.org>
Date: Thu, 22 Jun 2023 09:11:17 -0400
From: Joel Fernandes <joel@...lfernandes.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, vincent.guittot@...aro.org,
linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
mgorman@...e.de, bristot@...hat.com, corbet@....net,
qyousef@...alina.io, chris.hyser@...cle.com,
patrick.bellasi@...bug.net, pjt@...gle.com, pavel@....cz,
qperret@...gle.com, tim.c.chen@...ux.intel.com, joshdon@...gle.com,
timj@....org, kprateek.nayak@....com, yu.c.chen@...el.com,
youssefesmat@...omium.org, efault@....de, tglx@...utronix.de
Subject: Re: [PATCH 08/15] sched: Commit to EEVDF
On 6/22/23 08:01, Ingo Molnar wrote:
>
> * Joel Fernandes <joel@...lfernandes.org> wrote:
>
>> On Wed, May 31, 2023 at 01:58:47PM +0200, Peter Zijlstra wrote:
>>> EEVDF is a better defined scheduling policy, as a result it has less
>>> heuristics/tunables. There is no compelling reason to keep CFS around.
>>>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> ---
>>> kernel/sched/debug.c | 6
>>> kernel/sched/fair.c | 465 +++---------------------------------------------
>>
>> Whether EEVDF helps us improve our CFS latency issues or not, I do like the
>> merits of this diffstat alone and the lesser complexity and getting rid of
>> those horrible knobs is kinda nice.
>
> To to be fair, the "removal" in this patch is in significant part an
> artifact of the patch series itself, because first EEVDF bits get added by
> three earlier patches, in parallel to CFS:
>
> kernel/sched/fair.c | 137 +++++++++++++++++++++++++++++++++++++++++++++++++--
> kernel/sched/fair.c | 162 +++++++++++++++++++++++++++++++++++++-----------
> kernel/sched/fair.c | 338 +++++++++++++++++++++++++++++++++++++++++-------
>
> ... and then we remove the old CFS policy code in this 'commit to EEVDF' patch:
>
> kernel/sched/fair.c | 465 +++---------------------------------------------
>
> The combined diffstat is close to 50% / 50% balanced:
>
> kernel/sched/fair.c | 1105 ++++++++++++++++++--------------------
>
> But having said that, I do agree that EEVDF as submitted by Peter is better
> defined, with fewer heuristics, which is an overall win - so no complaints
> from me!
Agreed, thank you for correcting me on the statistics.
- Joel
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