Date: Tue, 15 Sep 2009 21:15:07 +0100 (BST)
From: Hugh Dickins <hugh.dickins@tiscali.co.uk>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>,
       Andrew Morton <akpm@linux-foundation.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Nick Piggin <npiggin@suse.de>, Rik van Riel <riel@redhat.com>,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 7/8] mm: reinstate ZERO_PAGE
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On Wed, 9 Sep 2009, KAMEZAWA Hiroyuki wrote:
> On Tue, 8 Sep 2009 12:56:57 +0100 (BST)
> Hugh Dickins <hugh.dickins@tiscali.co.uk> wrote:
> > 
> > Though I like that we don't _need_ to change mlock.c for reinstated
> > ZERO_PAGE, this morning I'm having trouble persuading myself that
> > mlocking a readonly anonymous area is too silly to optimize for.
> > 
> > Maybe the very people who persuaded you to bring back the anonymous
> > use of ZERO_PAGE, are also doing a huge mlock of the area first?
> No, as far as I know, they'll not do huge mlock.

Thanks for that (not entirely conclusive!) info.

I've decided for the moment to make a couple of further optimizations
in mlock.c (along with the comment you asked for), and leave adding
another __get_user_pages flag until a case for it is demonstrated.

Small patch series following shortly.

Hugh
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