linux-kernel - Re: [PATCH 1/6] cpuidle: teo: Increase util-threshold

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Message-ID: <19d87e24-7c2b-4396-9514-74150b896cf3@arm.com>
Date: Fri, 7 Jun 2024 10:01:35 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Christian Loehle <christian.loehle@....com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, rafael@...nel.org
Cc: vincent.guittot@...aro.org, qyousef@...alina.io, peterz@...radead.org,
 daniel.lezcano@...aro.org, anna-maria@...utronix.de,
 kajetan.puchalski@....com, lukasz.luba@....com
Subject: Re: [PATCH 1/6] cpuidle: teo: Increase util-threshold

On 06/06/2024 11:00, Christian Loehle wrote:
> Increase the util-threshold by a lot as it was low enough for some
> minor load to always be active, especially on smaller CPUs.

We see the blocked part of the CPU utilization as something telling the
task scheduler that the corresponding tasks might be runnable soon again
on this CPU.

This model seems to be used here as well. I guess folks are still
debating whether the amount of blocked utilization is a good enough
indicator for the length of idle time.

> For small cap CPUs (Pixel6) the util threshold is as low as 1.
> For CPUs of capacity <64 it is 0. So ensure it is at a minimum, too.

So before this threshold was 16 on a 1024 CPU, now it's 256?

A <= 200 CPU has now a threshold of 50.

Where do those numbers come from? Just from running another workload on
a specific device?

[...]