linux-kernel - Re: [PATCH] rmap: add exclusively owned pages to the newest anon

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Message-ID: <20100415083424.GA3565@liondog.tnic>
Date:	Thu, 15 Apr 2010 10:34:24 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Rik van Riel <riel@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	sgunderson@...foot.com
Subject: Re: [PATCH] rmap: add exclusively owned pages to the newest
 anon_vma

From: Rik van Riel <riel@...hat.com>
Date: Wed, Apr 14, 2010 at 05:59:28PM -0400

> The recent anon_vma fixes cause many anonymous pages to end up
> in the parent process anon_vma, even when the page is exclusively
> owned by the current process.
> 
> Adding exclusively owned anonymous pages to the top anon_vma
> reduces rmap scanning overhead, especially in workloads with
> forking servers.
> 
> This patch adds a parameter to __page_set_anon_rmap that can
> be used to indicate whether or not the added page is exclusively
> owned by the current process.
> 
> Pages added through page_add_new_anon_rmap are exclusively
> owned by the current process, and can be added to the top
> anon_vma.
> 
> Pages added through page_add_anon_rmap can be either shared
> or exclusively owned, so we do the conservative thing and
> add it to the oldest anon_vma.
> 
> A next step would be to add the exclusive parameter to
> page_add_anon_rmap, to be used from functions where we do
> know for sure whether a page is exclusively owned.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>
> ---
> Borislav, I audited the code before making this change, but would
> still appreciate your testing of this patch :)

Just did some light hammering and it looks ok so far. I'll keep watching
out for oopsies/issues.

Lightly-tested-by: Borislav Petkov <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.
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