linux-kernel - Re: [PATCH 08/19] mm: numa: Create basic numa page hinting infrastructure

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Message-ID: <20121113134910.GB17782@gmail.com>
Date:	Tue, 13 Nov 2012 14:49:10 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/19] mm: numa: Create basic numa page hinting
 infrastructure


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

> > But given that most architectures will be just fine reusing 
> > the already existing generic PROT_NONE machinery, the far 
> > better approach is to do what we've been doing in generic 
> > kernel code for the last 10 years: offer a default generic 
> > version, and then to offer per arch hooks on a strict 
> > as-needed basis, if they want or need to do something weird 
> > ...
> 
> If they are *not* fine with it, it's a large retrofit because 
> the PROT_NONE machinery has been hard-coded throughout. [...]

That was a valid criticism for earlier versions of the NUMA 
patches - but should much less be the case in the latest 
iterations of the patches:

 - it has generic pte_numa() / pmd_numa() instead of using
   prot_none() directly

 - the key utility functions are named using the _numa pattern,
   not *_prot_none*() anymore.

Let us know if you can still see such instances - it's probably 
simple oversight.

Thanks,

	Ingo
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