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Date: Wed, 4 Apr 2007 18:07:15 +0200
From: Andrea Arcangeli <andrea@suse.de>
To: Hugh Dickins <hugh@veritas.com>
Cc: Dan Aloni <da-x@monatomic.org>, Nick Piggin <npiggin@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Linux Memory Management List <linux-mm@kvack.org>, tee@sgi.com,
       holt@sgi.com, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [rfc] no ZERO_PAGE?
Message-ID: <20070404160715.GJ19587@v2.random>
References: <20070404033726.GE18507@wotan.suse.de> <Pine.LNX.4.64.0704041023040.17341@blonde.wat.veritas.com> <20070404102407.GA529@wotan.suse.de> <20070404122701.GB19587@v2.random> <20070404135530.GA29026@localdomain> <20070404141457.GF19587@v2.random> <20070404144421.GA13762@localdomain> <Pine.LNX.4.64.0704041553220.18202@blonde.wat.veritas.com> <20070404153451.GH19587@v2.random> <Pine.LNX.4.64.0704041636550.22242@blonde.wat.veritas.com>
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On Wed, Apr 04, 2007 at 04:41:46PM +0100, Hugh Dickins wrote:
> Nor I: I meant that anonymous readfault should
> (perhaps) mark the pte writable but clean.

Sorry I assumed when you said clean you implied readonly... Though
we'd need to differentiate the archs where the dirty bit is not set by
the hardware. Overall I'm unsure it worth it. Currently the VM
definitely wouldn't cope with a writeable and clean anonymous page, so
we'd need to change shrink_page_list and try_to_unmap_anon to make it
work. Likely it won't be measurable, so it may be a nice feature to
have from a theoretical point of view, in practice I doubt it matters.