linux-kernel - Re: [RFC] Track mlock()ed pages

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Date:	Fri, 26 Jan 2007 23:00:05 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...l.org>
CC:	Christoph Lameter <clameter@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] Track mlock()ed pages

Andrew Morton wrote:
> On Thu, 25 Jan 2007 22:36:17 -0800 (PST)
> Christoph Lameter <clameter@....com> wrote:
> 

>>>I can't think of an easy way to do this without per-page state. ie.
>>>another page flag.
>>
>>Thats what I am trying to avoid.
> 
> 
> You could perhaps go for a walk across all the other vmas which presently
> map this page.  If any of them have VM_LOCKED, don't increment the counter.
> Similar on removal: only decrement the counter when the final mlocked VMA
> is dropping the pte.

Can't do with un-racily because you can't get that information
atomically, AFAIKS. When / if we ever lock the page in fault handler,
this could become easier... but that seems nasty to do in fault path,
even if only for VM_LOCKED vmas.

-- 
SUSE Labs, Novell Inc.
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