linux-kernel - Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity

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Date:	Sat, 12 Sep 2015 02:24:51 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	bsegall@...gle.com
Cc:	Morten Rasmussen <morten.rasmussen@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Steve Muckle <steve.muckle@...aro.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"mturquette@...libre.com" <mturquette@...libre.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <Juri.Lelli@....com>,
	"sgurrappadi@...dia.com" <sgurrappadi@...dia.com>,
	"pang.xunlei@....com.cn" <pang.xunlei@....com.cn>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by
 capacity_orig

On Fri, Sep 11, 2015 at 10:05:53AM -0700, bsegall@...gle.com wrote:
> 
> SCHED_LOAD_RESOLUTION and the non-SLR part of SCHED_LOAD_SHIFT are not
> required to be the same value and should not be conflated.
 
> In particular, since cgroups are on the same timeline as tasks and their
> shares are not scaled by SCHED_LOAD_SHIFT in any way (but are scaled so
> that SCHED_LOAD_RESOLUTION is invisible), changing that part of
> SCHED_LOAD_SHIFT would cause issues, since things can assume that nice-0
> = 1024. However changing SCHED_LOAD_RESOLUTION would be fine, as that is
> an internal value to the kernel.
>
> In addition, changing the non-SLR part of SCHED_LOAD_SHIFT would require
> recomputing all of prio_to_weight/wmult for the new NICE_0_LOAD.

Not fully looked into the concerns, but the new SCHED_RESOLUTION_SHIFT
is intended to formalize all the integer metrics that need better resolution.
It is not special to any metric, so actually it is to de-conflate whoever is
conflated.
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