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Re: [PATCH 08/14] Memory compaction core

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From: Mel Gorman
Subject: Re: [PATCH 08/14] Memory compaction core
Date: Thursday, April 8, 2010 - 9:59 am

On Fri, Apr 02, 2010 at 05:02:42PM +0100, Mel Gorman wrote:

When merging compaction and transparent huge pages, Andrea spotted and
fixed this problem in his tree but it should go to mmotm as well.

Thanks Andrea.

==== CUT HERE ====
mm,compaction: page buddy can go away before reading page_order while isolating pages for migration

From: Andrea Arcangeli <aarcange@redhat.com>

zone->lock isn't held so the optimisation is unsafe. The page could be
allocated between when PageBuddy is checked and page-order is called. The
scanner will harmlessly walk the other free pages so let's just skip this
optimization.

This is a fix to the patch "Memory compaction core".

[mel@csn.ul.ie: Expanded the changelog]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>

---
 mm/compaction.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index dadad52..4fb33f6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -262,10 +262,8 @@ static unsigned long isolate_migratepages(struct zone *zone,
 
 		/* Get the page and skip if free */
 		page = pfn_to_page(low_pfn);
-		if (PageBuddy(page)) {
-			low_pfn += (1 << page_order(page)) - 1;
+		if (PageBuddy(page))
 			continue;
-		}
 
 		/* Try isolate the page */
 		if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
--
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Messages in current thread:
[PATCH 0/14] Memory Compaction v7, Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 03/14] mm: Share the anon_vma ref counts between KS ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 04/14] Allow CONFIG_MIGRATION to be set without CON ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 05/14] Export unusable free space index via /proc/u ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 06/14] Export fragmentation index via /proc/extfrag ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 07/14] Move definition for LRU isolation modes to a ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 08/14] Memory compaction core, Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 09/14] Add /proc trigger for memory compaction, Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 10/14] Add /sys trigger for per-node memory compaction, Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 11/14] Direct compact when a high-order allocation ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 12/14] Add a tunable that decides when memory shoul ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 13/14] Do not compact within a preferred zone after ..., Mel Gorman, (Fri Apr 2, 9:02 am)
[PATCH 14/14] mm,migration: Allow the migration of PageSwa ..., Mel Gorman, (Fri Apr 2, 9:02 am)
Re: [PATCH 14/14] mm,migration: Allow the migration of Pag ..., KAMEZAWA Hiroyuki, (Mon Apr 5, 11:54 pm)
[No subject], Tarkan Erimer, (Tue Apr 6, 7:47 am)
[No subject], Mel Gorman, (Tue Apr 6, 8:00 am)
[No subject], Tarkan Erimer, (Tue Apr 6, 8:03 am)
[No subject], Minchan Kim, (Tue Apr 6, 8:37 am)
Re: [PATCH 10/14] Add /sys trigger for per-node memory com ..., Andrew Morton, (Tue Apr 6, 2:56 pm)
Re: [PATCH 03/14] mm: Share the anon_vma ref counts betwee ..., Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 04/14] Allow CONFIG_MIGRATION to be set without ..., Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 05/14] Export unusable free space index via /pr ..., Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 06/14] Export fragmentation index via /proc/ext ..., Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 08/14] Memory compaction core, Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 09/14] Add /proc trigger for memory compaction, Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 10/14] Add /sys trigger for per-node memory com ..., Andrew Morton, (Tue Apr 6, 5:05 pm)
Re: [PATCH 11/14] Direct compact when a high-order allocat ..., Andrew Morton, (Tue Apr 6, 5:06 pm)
Re: [PATCH 12/14] Add a tunable that decides when memory s ..., Andrew Morton, (Tue Apr 6, 5:06 pm)
Re: [PATCH 13/14] Do not compact within a preferred zone a ..., Andrew Morton, (Tue Apr 6, 5:06 pm)
Re: [PATCH 14/14] mm,migration: Allow the migration of Pag ..., Andrew Morton, (Tue Apr 6, 5:06 pm)
Re: [PATCH 03/14] mm: Share the anon_vma ref counts betwee ..., Rik van Riel, (Tue Apr 6, 5:10 pm)
Re: [PATCH 10/14] Add /sys trigger for per-node memory com ..., KAMEZAWA Hiroyuki, (Tue Apr 6, 5:31 pm)
Re: [PATCH 13/14] Do not compact within a preferred zone a ..., Andrea Arcangeli, (Tue Apr 6, 5:55 pm)
Re: [PATCH 10/14] Add /sys trigger for per-node memory com ..., KAMEZAWA Hiroyuki, (Tue Apr 6, 6:19 pm)
Re: [PATCH 03/14] mm: Share the anon_vma ref counts betwee ..., Mel Gorman, (Wed Apr 7, 3:01 am)
Re: [PATCH 04/14] Allow CONFIG_MIGRATION to be set without ..., Mel Gorman, (Wed Apr 7, 3:22 am)
Re: [PATCH 05/14] Export unusable free space index via /pr ..., Mel Gorman, (Wed Apr 7, 3:35 am)
Re: [PATCH 06/14] Export fragmentation index via /proc/ext ..., Mel Gorman, (Wed Apr 7, 3:46 am)
Re: [PATCH 08/14] Memory compaction core, Mel Gorman, (Wed Apr 7, 8:21 am)
Re: [PATCH 09/14] Add /proc trigger for memory compaction, Mel Gorman, (Wed Apr 7, 8:39 am)
Re: [PATCH 10/14] Add /sys trigger for per-node memory com ..., Mel Gorman, (Wed Apr 7, 8:42 am)
Re: [PATCH 11/14] Direct compact when a high-order allocat ..., Mel Gorman, (Wed Apr 7, 9:06 am)
Re: [PATCH 12/14] Add a tunable that decides when memory s ..., Mel Gorman, (Wed Apr 7, 9:11 am)
Re: [PATCH 13/14] Do not compact within a preferred zone a ..., Mel Gorman, (Wed Apr 7, 9:32 am)
Re: [PATCH 14/14] mm,migration: Allow the migration of Pag ..., Mel Gorman, (Wed Apr 7, 9:49 am)
Re: [PATCH 09/14] Add /proc trigger for memory compaction, Mel Gorman, (Wed Apr 7, 11:27 am)
Re: [PATCH 11/14] Direct compact when a high-order allocat ..., Mel Gorman, (Wed Apr 7, 11:29 am)
Re: [PATCH 08/14] Memory compaction core, Mel Gorman, (Thu Apr 8, 9:59 am)
Re: [PATCH 08/14] Memory compaction core, Andrea Arcangeli, (Thu Apr 8, 10:06 am)
Re: [PATCH 05/14] Export unusable free space index via /pr ..., Mel Gorman, (Tue Apr 13, 5:42 am)
Re: [PATCH 06/14] Export fragmentation index via /proc/ext ..., Mel Gorman, (Tue Apr 13, 5:43 am)