From: Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0
Date: Thu, 12 May 2011 13:00:10 -0500 (CDT)
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Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
	Dave Jones <davej@redhat.com>, Mel Gorman <mgorman@suse.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Colin King <colin.king@canonical.com>,
	Raghavendra D Prabhu <raghu.prabhu13@gmail.com>,
	Jan Kara <jack@suse.cz>, Chris Mason <chris.mason@oracle.com>,
	Pekka Enberg <penberg@kernel.org>,
	Rik van Riel <riel@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-ext4 <linux-ext4@vger.kernel.org>
To: Andrea Arcangeli <aarcange@redhat.com>
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On Thu, 12 May 2011, Andrea Arcangeli wrote:

> order 1 should work better, because it's less likely we end up here
> (which leaves RECLAIM_MODE_LUMPYRECLAIM on and then see what happens
> at the top of page_check_references())
>
>    else if (sc->order && priority < DEF_PRIORITY - 2)

Why is this DEF_PRIORITY - 2? Shouldnt it be DEF_PRIORITY? An accomodation
for SLAB order 1 allocs?

May I assume that the case of order 2 and 3 allocs in that case was not
very well tested after the changes to introduce compaction since people
were focusing on RHEL testing?