linux-kernel - Re: [PATCH v3] mm: make expand_downwards symmetrical to expand

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Message-ID: <20110420192540.GC31296@parisc-linux.org>
Date:	Wed, 20 Apr 2011 13:25:41 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Christoph Lameter <cl@...ux.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Pekka Enberg <penberg@...nel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	linux-parisc@...r.kernel.org, David Rientjes <rientjes@...gle.com>,
	Ingo Molnar <mingo@...e.hu>, x86 maintainers <x86@...nel.org>,
	linux-arch@...r.kernel.org, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH v3] mm: make expand_downwards symmetrical to
	expand_upwards

On Wed, Apr 20, 2011 at 10:22:04AM -0500, Christoph Lameter wrote:
> There is barely any testing going on at all of this since we have had this
> issue for more than 5 years and have not noticed it. The absence of bug
> reports therefore proves nothing. Code inspection of the VM shows
> that this is an issue that arises in multiple subsystems and that we have
> VM_BUG_ONs in the page allocator that should trigger for these situations.

So ... we've proven that people using these architectures use SLAB
instead of SLUB, don't enable CONFIG_DEBUG_VM and don't use hugepages
(not really a surprise ... nobody's running Oracle on these arches :-)

I don't think that qualifies as "barely any testing".  I think that's
"nobody developing the Linux MM uses one of these architectures".

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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