linux-kernel - Re: [PATCH 00/27] Latest numa/core release, v16

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Message-ID: <20121121174015.GA29331@gmail.com>
Date:	Wed, 21 Nov 2012 18:40:15 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 00/27] Latest numa/core release, v16


* Ingo Molnar <mingo@...nel.org> wrote:

> So because I did not have an old-glibc system like David's, I 
> did not know the actual page fault rate. If it is high enough 
> then nonlinear effects might cause such effects.
> 
> This is an entirely valid line of inquiry IMO.

Btw., when comparing against 'mainline' I routinely use a 
vanilla kernel that has the same optimization applied. (first I 
make sure it's not a regression to vanilla.)

I do that to factor out the linear component of the independent 
speedup: it would not be valid to compare vanilla against 
numa/core+optimization, but the comparison has to be:

       vanilla + optimization
  vs.
     numa/core + optimization

I did that with last night's numbers as well.

So any of this can only address a regression if a non-linear 
factor is in play.

Since I have no direct access to a regressing system I have to 
work with the theories that I can think of: one had a larger 
effect, the other had a smaller effect, the third one had no 
effect on David's system.

How would you have done it instead?

Thanks,

	Ingo
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