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

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Message-Id: <20240716141645.637620-1-mfleming@cloudflare.com>
Date: Tue, 16 Jul 2024 15:16:45 +0100
From: Matt Fleming <matt@...dmodwrite.com>
To: 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
Subject: Re: [RFC PATCH 0/7] Optimization to reduce the cost of newidle balance

> Hi,
> 
> This is the second version of the newidle balance optimization[1].
> It aims to reduce the cost of newidle balance which is found to
> occupy noticeable CPU cycles on some high-core count systems.

Hi there, what's the status of this series?

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.

Thanks,
Matt