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

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Date:	Wed, 21 Nov 2012 19:04:32 +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


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> [...] And not look at vsyscalls or anything, but look at what 
> schednuma does wrong!

I have started 4 independent lines of inquiry to figure out 
what's wrong on David's system, and all four are in the category 
of 'what does our tree do to cause a regression':

  - suboptimal (== regressive) 4K fault handling by numa/core

  - suboptimal (== regressive) placement by numa/core on David's 
    assymetric-topology system

  - vsyscalls escallating numa/core page fault overhead
    non-linearly

  - TLB flushes escallating numacore page fault overhead
    non-linearly

I have sent patches for 3 of them, one is still work in 
progress, because it's non-trivial.

I'm absolutely open to every possibility and obviously any 
regression is numa/core's fault, full stop.

What would you have done differently to handle this particular 
regression?

Thanks,

	Ingo
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