linux-kernel - Re: [PATCH 4/2] numa, mm: Rename the PROT

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Message-ID: <20121021134341.GA23820@gmail.com>
Date:	Sun, 21 Oct 2012 15:43:41 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, mingo@...hat.com,
	linux-kernel@...r.kernel.org, aarcange@...hat.com,
	Michel Lespinasse <walken@...gle.com>
Subject: Re: [PATCH 4/2] numa, mm: Rename the PROT_NONE fault handling
 functions


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

> > Michel indicated that he does not use PROT_NONE for his 
> > working set estimation code, but instead checks the accessed 
> > bits in the page tables.
> 
> The pte_young() WSS method has a couple of fundamental 
> limitations:
> 
>  - it doesn't work with shared memory very well, the pte is per
>    mapping, not per page. The PROT_NONE method instruments the
>    physical page in essence.
> 
>  - it does not tell us which task touched the pte, in a
>    multi-threaded program
> 
> So like Peter I'd too expect these new WSS methods to eventually 
> be picked up for any serious WSS work.

Nevertheless lets wait and see until it actually happens - and 
meanwhile the prot_none namings are confusing.

So I've applied your patch as-is, with two more (new) usage 
sites converted as well. Will push it out after a bit of 
testing.

Thanks,

	Ingo
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