Date: Wed, 22 Jan 2014 22:09:10 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>, Mel Gorman <mgorman@suse.de>,
        Pavel Emelyanov <xemul@parallels.com>, gnome@rvzt.net,
        drawoc@darkrefraction.com, alan@lxorguk.ukuu.org.uk,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        bugzilla-daemon@bugzilla.kernel.org
Subject: Re: [Bug 67651] Bisected: Lots of fragmented mmaps cause gimp to
 fail in 3.12 after exceeding vm_max_map_count
Message-Id: <20140122220910.198121ee.akpm@linux-foundation.org>
In-Reply-To: <20140123055906.GS1574@moon>
References: <20140122190816.GB4963@suse.de>
	<52E04A21.3050101@mit.edu>
	<20140123055906.GS1574@moon>
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Sender: linux-kernel-owner@vger.kernel.org

On Thu, 23 Jan 2014 09:59:06 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> On Wed, Jan 22, 2014 at 02:45:53PM -0800, Andy Lutomirski wrote:
> > >     
> > >     Thus when user space application track memory changes now it can detect if
> > >     vma area is renewed.
> > 
> > Presumably some path is failing to set VM_SOFTDIRTY, thus preventing mms
> > from being merged.
> > 
> > That being said, this could cause vma blowups for programs that are
> > actually using this thing.
> 
> Hi Andy, indeed, this could happen. The easiest way is to ignore softdirty bit
> when we're trying to merge vmas and set it one new merged. I think this should
> be correct. Once I finish I'll send the patch.

Hang on.  We think the problem is that gimp is generating vmas which
*should* be merged, but for unknown reasons they differ in
VM_SOFTDIRTY, yes?

Shouldn't we work out where we're forgetting to set VM_SOFTDIRTY? 
Putting bandaids over this error when we come to trying to merge the
vmas sounds very wrong?
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