linux-kernel - [ 19/41] mm: compaction: make isolate_lru

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Date:	Mon, 30 Jul 2012 10:31:18 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Minchan Kim <minchan.kim@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: [ 19/41] mm: compaction: make isolate_lru_page() filter-aware

From: Greg KH <gregkh@...uxfoundation.org>

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Minchan Kim <minchan.kim@...il.com>

commit 39deaf8585152f1a35c1676d3d7dc6ae0fb65967 upstream.

Stable note: Not tracked in Bugzilla. THP and compaction disrupt the LRU
	list leading to poor reclaim decisions which has a variable
	performance impact.

In async mode, compaction doesn't migrate dirty or writeback pages.  So,
it's meaningless to pick the page and re-add it to lru list.

Of course, when we isolate the page in compaction, the page might be dirty
or writeback but when we try to migrate the page, the page would be not
dirty, writeback.  So it could be migrated.  But it's very unlikely as
isolate and migration cycle is much faster than writeout.

So, this patch helps cpu overhead and prevent unnecessary LRU churning.

Signed-off-by: Minchan Kim <minchan.kim@...il.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Acked-by: Mel Gorman <mgorman@...e.de>
Acked-by: Rik van Riel <riel@...hat.com>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/mmzone.h |    2 ++
 mm/compaction.c        |    7 +++++--
 mm/vmscan.c            |    3 +++
 3 files changed, 10 insertions(+), 2 deletions(-)

--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -162,6 +162,8 @@ static inline int is_unevictable_lru(enu
 #define ISOLATE_INACTIVE	((__force isolate_mode_t)0x1)
 /* Isolate active pages */
 #define ISOLATE_ACTIVE		((__force isolate_mode_t)0x2)
+/* Isolate clean file */
+#define ISOLATE_CLEAN		((__force isolate_mode_t)0x4)
 
 /* LRU Isolation modes. */
 typedef unsigned __bitwise__ isolate_mode_t;
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -261,6 +261,7 @@ static isolate_migrate_t isolate_migrate
 	unsigned long last_pageblock_nr = 0, pageblock_nr;
 	unsigned long nr_scanned = 0, nr_isolated = 0;
 	struct list_head *migratelist = &cc->migratepages;
+	isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
 
 	/* Do not scan outside zone boundaries */
 	low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
@@ -370,9 +371,11 @@ static isolate_migrate_t isolate_migrate
 			continue;
 		}
 
+		if (!cc->sync)
+			mode |= ISOLATE_CLEAN;
+
 		/* Try isolate the page */
-		if (__isolate_lru_page(page,
-				ISOLATE_ACTIVE|ISOLATE_INACTIVE, 0) != 0)
+		if (__isolate_lru_page(page, mode, 0) != 0)
 			continue;
 
 		VM_BUG_ON(PageTransCompound(page));
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1045,6 +1045,9 @@ int __isolate_lru_page(struct page *page
 
 	ret = -EBUSY;
 
+	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
+		return ret;
+
 	if (likely(get_page_unless_zero(page))) {
 		/*
 		 * Be careful not to clear PageLRU until after we're


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