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Message-Id: <20081002154446.3695a3b0.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 2 Oct 2008 15:44:46 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Andy Whitcroft <apw@...dowen.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Peter Zijlstra <peterz@...radead.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
Nick Piggin <nickpiggin@...oo.com.au>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/4] Reclaim page capture v4
On Wed, 1 Oct 2008 13:30:57 +0100
Andy Whitcroft <apw@...dowen.org> wrote:
> For sometime we have been looking at mechanisms for improving the availability
> of larger allocations under load. One of the options we have explored is
> the capturing of pages freed under direct reclaim in order to increase the
> chances of free pages coelescing before they are subject to reallocation
> by racing allocators.
>
> Following this email is a patch stack implementing page capture during
> direct reclaim. It consits of four patches. The first two simply pull
> out existing code into helpers for reuse. The third makes buddy's use
> of struct page explicit. The fourth contains the meat of the changes,
> and its leader contains a much fuller description of the feature.
>
> This update represents a rebase to -mm and incorporates feedback from
> KOSAKI Motohiro. It also incorporates an accounting fix which was
> preventing some captures.
>
> I have done a lot of comparitive testing with and without this patch
> set and in broad brush I am seeing improvements in hugepage allocations
> (worst case size) success on all of my test systems. These tests consist
> of placing a constant stream of high order allocations on the system,
> at varying rates. The results for these various runs are then averaged
> to give an overall improvement.
>
> Absolute Effective
> x86-64 2.48% 4.58%
> powerpc 5.55% 25.22%
>
> x86-64 has a relatively small huge page size and so is always much more
> effective at allocating huge pages. Even there we get a measurable
> improvement. On powerpc the huge pages are much larger and much harder
> to recover. Here we see a full 25% increase in page recovery.
>
> It should be noted that these are worst case testing, and very agressive
> taking every possible page in the system. It would be helpful to get
> wider testing in -mm.
>
> Against: 2.6.27-rc1-mm1
>
> Andrew, please consider for -mm.
>
Hmm, can't we use "MIGRATE_ISOLATE" pageblock type for this purpose ?
The page allocater skips pageblock marked as MIGRATE_ISOLATE at allocation.
(pageblock-size is equal to HUGEPAGE size in general.)
Of course, "where should be isolated" is a problem.
Thanks,
-Kame
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