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Date: Wed, 23 Apr 2003 23:36:52 -0400
From: Benjamin LaHaise <bcrl@redhat.com>
To: Andrew Morton <akpm@digeo.com>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org
Subject: Re: 2.5.68-mm2
Message-ID: <20030423233652.C9036@redhat.com>
References: <20030423012046.0535e4fd.akpm@digeo.com> <18400000.1051109459@[10.10.2.4]> <20030423144648.5ce68d11.akpm@digeo.com>
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In-Reply-To: <20030423144648.5ce68d11.akpm@digeo.com>; from akpm@digeo.com on Wed, Apr 23, 2003 at 02:46:48PM -0700
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On Wed, Apr 23, 2003 at 02:46:48PM -0700, Andrew Morton wrote:
> Ingo-rmap seems a better solution to me.  It would be a fairly large change
> though - we'd have to hold the four atomic kmaps across an entire pte page
> in copy_page_range(), for example.  But it will then have good locality of
> reference between adjacent pages and may well be quicker than pte_chains.

Actually, Ingo's rmap style sounds very similar to what I first implemented 
in one of my stabs at rmap.  It has a nasty side effect of being worst case 
for cache organisation -- the sister page tends to map to the exact same 
cache line in some processors.  Whoops.  That said, I think that the rmap 
pte-chains can really stand a bit of optimization by means of discarding a 
couple of bits, as well as merging for adjacent pages, so I don't think 
the overhead is a lost cause yet.  And nobody has written the clone() patch 
for bash yet...

		-ben
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