linux-kernel - Re: [RFC PATCH -v3] take all anon_vma locks in anon_vma

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Message-ID: <4BD9A84C.3050709@redhat.com>
Date:	Thu, 29 Apr 2010 11:39:56 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Minchan Kim <minchan.kim@...il.com>
CC:	Andrea Arcangeli <aarcange@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH -v3] take all anon_vma locks in anon_vma_lock

On 04/28/2010 10:55 PM, Minchan Kim wrote:

> When you tried anon_vma_chain patches as I pointed out, what I have a
> concern is parent's vma not child's one.
> The vma of parent still has N anon_vma.

No, it is the other way around.

The anon_vma of the parent is also present in all of the
children, so the parent anon_vma is attached to N vmas.

However, the parent vma only has 1 anon_vma attached to
it, and each of the children will have 2 anon_vmas.

That is what should keep any locking overhead with this
patch minimal.

Yes, a deep fork bomb can slow itself down.  Too bad,
don't do that :)

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