mm: compaction: make isolate_lru_page() filter-aware

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@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 436ce6e7a446b938355b5750f7a91261ce4eaf35..8cb7c0daae2f64cbf981c3ed574325f63fcd8e9f 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -168,6 +168,8 @@ static inline int is_unevictable_lru(enum lru_list l)
 #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 fmode_t)0x4)
 
 /* LRU Isolation modes. */
 typedef unsigned __bitwise__ isolate_mode_t;

diff --git a/mm/compaction.c b/mm/compaction.c
index 47f717fa42334552f6d57add946961549b734801..a0e420207ebff3778fc5c17136dc2d5176391105 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -261,6 +261,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
        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);
@@ -348,9 +349,11 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
                        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));

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ec6dbcb976d1b112f4f9a46178b59a0cc6fe7575..c007e78d7078c58c79908ba862628919780322d3 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1045,6 +1045,9 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
 
        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