Messages in this thread Patch in this message | | | Date | Thu, 8 Apr 2010 17:59:54 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 08/14] Memory compaction core |
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On Fri, Apr 02, 2010 at 05:02:42PM +0100, Mel Gorman wrote: > This patch is the core of a mechanism which compacts memory in a zone by > relocating movable pages towards the end of the zone. >
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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