linux-kernel - Re: [RFC PATCH 08/14] sched: normalize tg load contributions against runnable time

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Message-ID: <1329754219.2293.357.camel@twins>
Date:	Mon, 20 Feb 2012 17:10:19 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Paul Turner <pjt@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Venki Pallipadi <venki@...gle.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Mike Galbraith <efault@....de>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ben Segall <bsegall@...gle.com>, Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 08/14] sched: normalize tg load contributions
 against runnable time

On Fri, 2012-02-17 at 04:32 -0800, Paul Turner wrote:
> > Neither the comment nor the changelog mention this, it should, it should
> > also mention why it doesn't matter (does it?).
> 
> It doesn't and it should.  Although I'll take the liberty shortening
> it a little to something

For the in-code comment that's fine, it would be good for the changelog
to have the entire story though.

>  like "unfortunately we cannot compute
> runnable_avg(tg) directly, however, XXX is a reasonable
> approximation." 

Yeah, not easily done indeed, you could compute a corrective term if
you'd have something like the avg and variance of runnable over the
various CPUs, but those too suck to have to compute.


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