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Date: Thu, 28 Oct 2010 17:12:01 +0200
From: Andrea Arcangeli <aarcange@redhat.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>, LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Wu Fengguang <fengguang.wu@intel.com>,
        Minchan Kim <minchan.kim@gmail.com>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 4/7] vmscan: narrowing synchrounous lumply reclaim
 condition
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On Thu, Oct 28, 2010 at 05:00:57PM +0900, KOSAKI Motohiro wrote:
> Hi
> 
> > My tree uses compaction in a fine way inside kswapd too and tons of
> > systems are running without lumpy and floods of order 9 allocations
> > with only compaction (in direct reclaim and kswapd) without the
> > slighest problem. Furthermore I extended compaction for all
> > allocations not just that PAGE_ALLOC_COSTLY_ORDER (maybe I already
> > removed all PAGE_ALLOC_COSTLY_ORDER checks?). There's no good reason
> > not to use compaction for every allocation including 1,2,3, and things
> > works fine this way.
> 
> Interesting. I parsed this you have compaction improvement. If so,
> can you please post them? Generically, 1) improve the feature 2) remove
> unused one is safety order. In the other hand, reverse order seems to has
> regression risk.

THP is way higher priority than the compaction improvements, so the
compaction improvements are not at the top of the queue:

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=shortlog

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commitdiff;h=d8f02410d718725a7daaf192af33abc41dcfae16;hp=39c4a61fedc5f5bf0c95a60483ac0acea1a9a757

At the top of the queue there is the lumpy_reclaim removal as that's
higher priority than THP.