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

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Date:	Mon, 19 Nov 2012 23:36:04 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	linux-kernel@...r.kernel.org, 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>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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

* Mel Gorman <mgorman@...e.de> wrote:

> Ok.
> 
> In response to one of your later questions, I found that I had 
> in fact disabled THP without properly reporting it. [...]

Hugepages is a must for most forms of NUMA/HPC. This alone 
questions the relevance of most of your prior numa/core testing 
results. I now have to strongly dispute your other conclusions 
as well.

Just a look at 'perf top' output should have told you the story.

Yet time and time again you readily reported bad 'schednuma' 
results for a slow 4K memory model that neither we nor other 
NUMA testers I talked to actually used, without stopping to look 
why that was so...

[ I suspect that if such terabytes-of-data workloads are forced 
  through such a slow 4K pages model then there's a bug or 
  mis-tuning in our code that explains the level of additional 
  slowdown you saw - we'll fix that.

  But you should know that behavior under the slow 4K model 
  tells very little about the true scheduling and placement 
  quality of the patches... ]

Please report proper THP-enabled numbers before continuing.

Thanks,

	Ingo
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