linux-kernel - [PATCH] mm: skip watermarks check for already isolated blocks in split_free

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Message-id: <1352357944-14830-1-git-send-email-m.szyprowski@samsung.com>
Date:	Thu, 08 Nov 2012 07:59:04 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [PATCH] mm: skip watermarks check for already isolated blocks in
 split_free_page()

Since commit 2139cbe627b8 ("cma: fix counting of isolated pages") free
pages in isolated pageblocks are not accounted to NR_FREE_PAGES counters,
so watermarks check is not required if one operates on a free page in
isolated pageblock.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
---
 mm/page_alloc.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fd154fe..43ab09f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1394,10 +1394,12 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
 	zone = page_zone(page);
 	order = page_order(page);
 
-	/* Obey watermarks as if the page was being allocated */
-	watermark = low_wmark_pages(zone) + (1 << order);
-	if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
-		return 0;
+	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE) {
+		/* Obey watermarks as if the page was being allocated */
+		watermark = low_wmark_pages(zone) + (1 << order);
+		if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+			return 0;
+	}
 
 	/* Remove page from free list */
 	list_del(&page->lru);
-- 
1.7.9.5

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