linux-kernel - Re: Populating multiple ptes at fault time

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Message-ID: <48D17AEC.3070804@goop.org>
Date:	Wed, 17 Sep 2008 14:47:24 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rik van Riel <riel@...hat.com>
CC:	Nick Piggin <nickpiggin@...oo.com.au>,
	Hugh Dickens <hugh@...itas.com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Avi Kivity <avi@...ranet.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Populating multiple ptes at fault time

Rik van Riel wrote:
> On Wed, 17 Sep 2008 10:47:30 -0700
> Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>   
>> Minor faults are easier; if the page already exists in memory, we should
>> just create mappings to it.  If neighbouring pages are also already
>> present, then we can can cheaply create mappings for them too.
>>     
>
> This is especially true for mmaped files, where we do not have to
> allocate anything to create the mapping.
>   

Yes, that was the case I particularly had in mind.

> Populating multiple PTEs at a time is questionable for anonymous
> memory, where we'd have to allocate extra pages.
>   

It might be worthwhile if the memory access pattern to anonymous memory
is linear.  I agree that speculatively allocating pages on a random
access region would be a bad idea.

    J
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