linux-kernel - Re: [PATCH] sched/fair: Prevent cpu_busy_time from exceeding actual_cpu

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Message-ID: <CAB8ipk-E_LPmhHuYSXQuagdnitmtnobSG55kz5mZ_b-yF0XFUw@mail.gmail.com>
Date: Mon, 24 Jun 2024 10:35:53 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>, Qais Yousef <qyousef@...alina.io>, 
	Xuewen Yan <xuewen.yan@...soc.com>, mingo@...hat.com, peterz@...radead.org, 
	juri.lelli@...hat.com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com, 
	vincent.donnefort@....com, ke.wang@...soc.com, linux-kernel@...r.kernel.org, 
	christian.loehle@....com
Subject: Re: [PATCH] sched/fair: Prevent cpu_busy_time from exceeding actual_cpu_capacity

On Fri, Jun 21, 2024 at 9:01 PM Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> On Fri, 21 Jun 2024 at 12:41, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> >
> > On 19/06/2024 04:46, Xuewen Yan wrote:
> > > On Tue, Jun 18, 2024 at 10:58 PM Qais Yousef <qyousef@...alina.io> wrote:
> > >>
> > >> On 06/17/24 12:03, Qais Yousef wrote:
> >
> > [...]
> >
> > > Sorry for the late reply...
> > > In our own tree, we removed the check for rd overutil in feec(), so
> > > the above case often occurs.
> >
> > How to you schedule hackbench on this thing then? Via EAS or do you just
> > exclude this kind of workload?
>
> Don't know the details for Xuewen but that's also what I'm doing as
> part of the rework I'm doing on EAS. As I said in at OSPM, I'm also
> calling feec() every time even when overutilized. feec() return -1
> when it can't find a suitable cpu and we then fallback to default
> performance path
>
Aha, we do the same, We use eas on Android, and there is often only
one or two tasks in the overutil state, but we don't want this
scenario to affect the placement of other small tasks.
Only when all CPUs are in the overutil state, feec will return -1, and
then fallback to default performance path.

BR
---
xuewen