mm: compaction: compact unevictable pages

Presently compaction doesn't handle mlocked pages as it uses
__isolate_lru_page which doesn't consider unevicatable pages.  It is used
by just lumpy so it is pointless that it isolates unevictable pages.

But the situation has changed.  Compaction can handle unevictable pages
and it can help getting big contiguos pages in memory whcih is fragmented
by many pinned pages with mlock.

I tested this patch with following scenario.

1. A : allocate 80% anon pages in system
2. B : allocate 20% mlocked page in system
/* Maybe, mlocked pages are located in low pfn address */
3. kill A /* high pfn address are free */
4. echo 1 > /proc/sys/vm/compact_memory

old:

compact_blocks_moved 251
compact_pages_moved 44

new:

compact_blocks_moved 258
compact_pages_moved 412

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <jweiner@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 188cb2ffe8db2685a5b1b50e584026a1ffcfd9f6..82b505e003ae9773bc9f8cb9bbcfca131c83fb36 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -169,10 +169,12 @@ 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 unevictable pages */
+#define ISOLATE_UNEVICTABLE    ((__force isolate_mode_t)0x4)
 /* Isolate clean file */
-#define ISOLATE_CLEAN          ((__force isolate_mode_t)0x4)
+#define ISOLATE_CLEAN          ((__force isolate_mode_t)0x8)
 /* Isolate unmapped file */
-#define ISOLATE_UNMAPPED       ((__force isolate_mode_t)0x8)
+#define ISOLATE_UNMAPPED       ((__force isolate_mode_t)0x10)
 
 /* LRU Isolation modes. */
 typedef unsigned __bitwise__ isolate_mode_t;

diff --git a/mm/compaction.c b/mm/compaction.c
index a0e420207ebff3778fc5c17136dc2d5176391105..0e572d1b9889273154328db3b2a6d0c7e18a247e 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -261,7 +261,8 @@ 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;
+       isolate_mode_t mode = ISOLATE_ACTIVE| ISOLATE_INACTIVE |
+                               ISOLATE_UNEVICTABLE;
 
        /* Do not scan outside zone boundaries */
        low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b970f5c489fa6484a3e09ebe56be904904c67a31..ec83496ff754578a0eed77de8db52dd5de420fdf 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1038,12 +1038,7 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
        if (!all_lru_mode && !!page_is_file_cache(page) != file)
                return ret;
 
-       /*
-        * When this function is being called for lumpy reclaim, we
-        * initially look into all LRU pages, active, inactive and
-        * unevictable; only give shrink_page_list evictable pages.
-        */
-       if (PageUnevictable(page))
+       if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
                return ret;
 
        ret = -EBUSY;