Date: Fri, 12 Mar 2004 13:55:30 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Andrea Arcangeli <andrea@suse.de>
cc: William Lee Irwin III <wli@holomorphy.com>, Rik van Riel <riel@redhat.com>,
       Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>,
       <torvalds@osdl.org>, <linux-kernel@vger.kernel.org>
Subject: Re: anon_vma RFC2
In-Reply-To: <20040312132436.GT30940@dualathlon.random>
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On Fri, 12 Mar 2004, Andrea Arcangeli wrote:
> On Fri, Mar 12, 2004 at 04:46:38AM -0800, William Lee Irwin III wrote:
> > 
> > The case where mremap() creates rmap_chains is so rare I never ever saw
> > it happen in 6 months of regular practical use and testing. Their
> > creation could be triggered only by remap_file_pages().
> 
> did you try specweb with apache? that's super heavy mremap as far as I
> know (and it maybe using anon memory, and if not I certainly cannot
> exclude other apps are using mremap on significant amounts of anymous
> ram).

anonmm has no problem with most mremaps: the special case is for
mremap MAYMOVE of anon vmas _inherited from parent_ (same page at
different addresses in the different mms).  As I said before, it's
quite conceivable that this case never arises outside our testing
(but I'd be glad to be shown wrong, would make effort worthwhile).

Hugh

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