linux-kernel - Re: madvise(2) MADV

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Message-ID: <20080717102025.6b7f0e40@cuia.bos.redhat.com>
Date:	Thu, 17 Jul 2008 10:20:25 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Chris Snook <csnook@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Eric Rannaud <eric.rannaud@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: madvise(2) MADV_SEQUENTIAL behavior

On Wed, 16 Jul 2008 17:05:14 -0400
Chris Snook <csnook@...hat.com> wrote:

> > I believe that for mmap MADV_SEQUENTIAL, we will have to do
> > an unmap-behind from the fault path.  Not every time, but
> > maybe once per megabyte, unmapping the megabyte behind us.
> > 
> > That way the normal page cache policies (use once, etc) can
> > take care of page eviction, which should help if the file
> > is also in use by another process.
> 
> Wouldn't it just be easier to not move pages to the active list when 
> they're referenced via an MADV_SEQUENTIAL mapping?  

You want to check the MADV_SEQUENTIAL hint at pageout time and
discard the referenced bit from the pte?

> If we keep them on the inactive list, they'll be candidates for
> reclaiming

Only if we ignore the referenced bit.  Which I guess we can do.

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