linux-kernel - Re: [PATCH 0/2 v4] sched: Rewrite per entity runnable load average tracking

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Date:	Tue, 29 Jul 2014 15:06:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	Morten Rasmussen <morten.rasmussen@....com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"pjt@...gle.com" <pjt@...gle.com>,
	"bsegall@...gle.com" <bsegall@...gle.com>,
	"arjan.van.de.ven@...el.com" <arjan.van.de.ven@...el.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"alan.cox@...el.com" <alan.cox@...el.com>,
	"mark.gross@...el.com" <mark.gross@...el.com>,
	"fengguang.wu@...el.com" <fengguang.wu@...el.com>
Subject: Re: [PATCH 0/2 v4] sched: Rewrite per entity runnable load average
 tracking

On Tue, Jul 29, 2014 at 09:17:13AM +0800, Yuyang Du wrote:
> On Mon, Jul 28, 2014 at 12:38:12PM +0200, Peter Zijlstra wrote:
> > On Mon, Jul 28, 2014 at 03:02:37AM +0800, Yuyang Du wrote:
> > > > Another thing that might be an issue is that the blocked of a terminated
> > > > task lives on for quite a while until has decayed away.
> > > 
> > > Good point. To do so, if I read correctly, we need to hook do_exit(), but probably
> > > we are gonna encounter rq->lock issue.
> > > 
> > > What is the opinion/guidance from the maintainers/others?
> > 
> > So the entire point of this per entity tracking was to make sure load
> > numbers reflect reality. We account migrations etc., it would be weird
> > to then throw all that out the window and let task exit accumulate crap.
> > 
> 
> Yes. So I will hook up do_exit. 

There is sched_class::task_dead(), pjt wanted to use that for this.

> Hope I did it right. Likewise, also do group entity
> in group destroy and group offline? 

group destroy, yes. Offline should mostly fix itself already due to it
actively migrating the actual load around I think.
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