From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 0/3] Reduce impact to overall system of SLUB using
 high-order allocations
Date: Thu, 12 May 2011 20:04:57 +0200
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Cc: David Rientjes <rientjes@google.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>,
        Christoph Lameter <cl@linux.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: James Bottomley <James.Bottomley@HansenPartnership.com>
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Hi James!

On Wed, May 11, 2011 at 05:34:27PM -0500, James Bottomley wrote:
> Yes, but only once in all the testing.  With patches 1 and 2 the hang is

Weird patch 2 makes the large order allocation without ~__GFP_WAIT, so
even COMPACTION=y/n shouldn't matter anymore. Am I misreading
something Mel?

Removing ~__GFP_WAIT from patch 2 (and adding ~__GFP_REPEAT as a
correctness improvement) and setting COMPACTION=y also should work ok.

Removing ~__GFP_WAIT from patch 2 and setting COMPACTION=n is expected
not to work well.

But compaction should only make the difference if you remove
~__GFP_WAIT from patch 2.

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