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Date: Wed, 7 Mar 2007 10:50:35 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: =?ISO-8859-1?B?UOFkcmFpZw==?= Brady <P@draigBrady.com>
Cc: bert hubert <bert.hubert@netherlabs.nl>, Rik van Riel <riel@redhat.com>,
       linux-kernel@vger.kernel.org
Subject: Re: userspace pagecache management tool
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On Wed, 07 Mar 2007 11:39:02 +0000 Pádraig Brady <P@draigBrady.com> wrote:

> Andrew Morton wrote:
> > On Tue, 06 Mar 2007 12:10:49 +0000
> > P__draig Brady <P@draigBrady.com> wrote:
> >> Perhaps one could possibly just evict pages with _mapcount==0 ?
> > 
> > That is the present fadvise(FADV_DONTNEED) behaviour.
> 
> Ah right. It doesn't invalidate page_mapped() pages.

yup

> If that means it doesn't invalidate pages previously cached
> by other processes, then great.

It will do that.  This is why I point out that this userspace tool
could (easily) be enhanced to not invalidate pages which were
in pagecache prior to their being read by the managed application.