linux-kernel - Re: [RFC PATCH 0/7] Optimization to reduce the cost of newidle balance

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Message-ID: <CAENh_SQzWeViGDGsqZFZYaNooB3NBKQR7XOkYB26SGEq1cZ5FA@mail.gmail.com>
Date: Wed, 17 Jul 2024 16:31:06 +0100
From: Matt Fleming <matt@...dmodwrite.com>
To: Chen Yu <yu.c.chen@...el.com>
Cc: aaron.lu@...el.com, dietmar.eggemann@....com, gautham.shenoy@....com, 
	juri.lelli@...hat.com, kprateek.nayak@....com, linux-kernel@...r.kernel.org, 
	mgorman@...hsingularity.net, mingo@...hat.com, peterz@...radead.org, 
	tim.c.chen@...el.com, vincent.guittot@...aro.org, yu.chen.surf@...il.com, 
	yujie.liu@...el.com, kernel-team@...udflare.com, yunzhao@...udflare.com
Subject: Re: [RFC PATCH 0/7] Optimization to reduce the cost of newidle balance

On Wed, Jul 17, 2024 at 4:53 AM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Thanks for your interest in this patch series. The RFC patch series was sent
> out to seek for directions and to see if this issue is worthy to fix. Since
> you have encountered this issue as well and it seems to be generic issue,
> I'll rebase thie patch series and retest it on top of latest kernel and then
> send out a new version.

Great, thanks!

> > I'm seeing this same symptom of burning cycles in update_sd_lb_stats() on an
> > AMD EPYC 7713 machine (128 CPUs, 8 NUMA nodes). The machine is about 50% idle
> > and upadte_sd_lb_stats() sits as the first entry in perf top with about 3.62%
> > of CPU cycles.
>
> May I know what benchmark(test scenario) you are testing? I'd like to replicate
> this test on my machine as well.

Actually this isn't a benchmark -- this was observed on Cloudflare's
production machines. I'm happy to try out your series and report back.

Thanks,
Matt