linux-kernel - Re: [RFC PATCH] sched/eevdf: Return leftmost entity in pick

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Message-ID: <ZiKoWSlTD8oSWI0R@chenyu5-mobl2>
Date: Sat, 20 Apr 2024 01:22:33 +0800
From: Chen Yu <yu.c.chen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Xuewen Yan <xuewen.yan94@...il.com>, Abel Wu <wuyun.abel@...edance.com>,
	Ingo Molnar <mingo@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	Juri Lelli <juri.lelli@...hat.com>, Tim Chen <tim.c.chen@...el.com>, "Tiwei
 Bie" <tiwei.btw@...group.com>, Honglei Wang <wanghonglei@...ichuxing.com>,
	Aaron Lu <aaron.lu@...el.com>, Chen Yu <yu.chen.surf@...il.com>, Yujie Liu
	<yujie.liu@...el.com>, <linux-kernel@...r.kernel.org>, kernel test robot
	<oliver.sang@...el.com>, Tianchen Ding <dtcccc@...ux.alibaba.com>
Subject: Re: [RFC PATCH] sched/eevdf: Return leftmost entity in pick_eevdf()
 if no eligible entity is found

On 2024-04-19 at 18:24:28 +0200, Peter Zijlstra wrote:
> On Fri, Apr 19, 2024 at 06:04:25PM +0800, Chen Yu wrote:
> 
> > > Also, could you put a few words in on how often these clips are hit? I
> > > suspect it's fairly rare (but crucial when it does).
> > 
> > Everytime it happens a subsequent NULL pointer exception usually happens.
> > The trace data was posted here: 
> 
> That was not the question. Suppose I put a printk whenever the clamp()
> actually changes the value, do I get a stormflood of output, or do I get
> a sporadic blip.

I see, it is not a frequent clamp - around 5~30 clamp per CPU every second,
when running trinity.

thanks,
Chenyu