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Date: Thu, 15 Mar 2007 14:35:17 -0400
From: Rik van Riel <riel@redhat.com>
Organization: Red Hat, Inc
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To: Valdis.Kletnieks@vt.edu
CC: Andreas Mohr <andi@rhlx01.fht-esslingen.de>,
       Dave Kleikamp <shaggy@linux.vnet.ibm.com>,
       Ashif Harji <asharji@cs.uwaterloo.ca>, linux-mm@kvack.org,
       Nick Piggin <npiggin@suse.de>, Jan Kara <jack@suse.cz>,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed
References: <Pine.GSO.4.64.0703081612290.1080@cpu102.cs.uwaterloo.ca> <20070312142012.GH30777@atrey.karlin.mff.cuni.cz> <20070312143900.GB6016@wotan.suse.de> <20070312151355.GB23532@duck.suse.cz> <Pine.GSO.4.64.0703121247210.7679@cpu102.cs.uwaterloo.ca> <20070312173500.GF23532@duck.suse.cz> <Pine.GSO.4.64.0703131438580.8193@cpu102.cs.uwaterloo.ca> <20070313185554.GA5105@duck.suse.cz> <Pine.GSO.4.64.0703141218530.28958@cpu102.cs.uwaterloo.ca> <1173905741.8763.36.camel@kleikamp.austin.ibm.com>            <20070314213317.GA22234@rhlx01.hs-esslingen.de> <200703151737.l2FHb81d001600@turing-police.cc.vt.edu>
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Valdis.Kletnieks@vt.edu wrote:
> On Wed, 14 Mar 2007 22:33:17 BST, Andreas Mohr said:
> 
>> it'd seem we need some kind of state management here to figure out good
>> intervals of when to call mark_page_accessed() *again* for this page. E.g.
>> despite non-changing access patterns you could still call mark_page_accessed(
> )
>> every 32 calls or so to avoid expiry, but this would need extra helper
>> variables.
> 
> What if you did something like
> 
> 	if (jiffies%32) {...
> 
> (Possibly scaling it so the low-order bits change).  No need to lock it, as
> "right most of the time" is close enough.

Bad idea.  That way you would only count page accesses if the
phase of the moon^Wjiffie is just right.

-- 
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