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

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Message-ID: <20140730004007.GC28673@intel.com>
Date:	Wed, 30 Jul 2014 08:40:07 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vincent Guittot <vincent.guittot@...aro.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Turner <pjt@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>,
	arjan.van.de.ven@...el.com, Len Brown <len.brown@...el.com>,
	rafael.j.wysocki@...el.com, alan.cox@...el.com,
	"Gross, Mark" <mark.gross@...el.com>,
	"fengguang.wu@...el.com" <fengguang.wu@...el.com>
Subject: Re: [PATCH 2/2 v4] sched: Rewrite per entity runnable load average
 tracking

On Wed, Jul 30, 2014 at 10:30:08AM +0200, Peter Zijlstra wrote:
> > 
> > Isn't the entire effort starting from PJT and Ben up to now to soften the extremely
> > dynamic changes (runnable or not, weight change, etc)? Assume task does not change
> > weight much, but group entity does as Peter mentioned.
> 
> No, softening isn't the point at all. But an integrator is the only
> means of predicting the future given the erratic past.
> 
> The whole point we got into this game is to better compute per cpu group
> weights, not to soften stuff, that's just a necessarily evil to more
> accurately predict erratic/unknown behaviour.
> 
> 
Yes, I totally agree. I think what I meant by "soften" is the *effect* of the integrator
that takes/averages the infinite history to predict the tufure.

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