From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id AC153600337 for ; Thu, 8 Apr 2010 13:00:19 -0400 (EDT) Date: Thu, 8 Apr 2010 17:59:54 +0100 From: Mel Gorman Subject: Re: [PATCH 08/14] Memory compaction core Message-ID: <20100408165954.GI25756@csn.ul.ie> References: <1270224168-14775-1-git-send-email-mel@csn.ul.ie> <1270224168-14775-9-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1270224168-14775-9-git-send-email-mel@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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 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 --- 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) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org