mm: compaction: memory compaction core

This patch is the core of a mechanism which compacts memory in a zone by
relocating movable pages towards the end of the zone.

A single compaction run involves a migration scanner and a free scanner.
Both scanners operate on pageblock-sized areas in the zone.  The migration
scanner starts at the bottom of the zone and searches for all movable
pages within each area, isolating them onto a private list called
migratelist.  The free scanner starts at the top of the zone and searches
for suitable areas and consumes the free pages within making them
available for the migration scanner.  The pages isolated for migration are
then migrated to the newly isolated free pages.

[aarcange@redhat.com: Fix unsafe optimisation]
[mel@csn.ul.ie: do not schedule work on other CPUs for compaction]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
new file mode 100644
index 000000000000..465ca88615ed
--- /dev/null
+++ b/include/linux/compaction.h
@@ -0,0 +1,9 @@
+#ifndef _LINUX_COMPACTION_H
+#define _LINUX_COMPACTION_H
+
+/* Return values for compact_zone() */
+#define COMPACT_CONTINUE        0
+#define COMPACT_PARTIAL         1
+#define COMPACT_COMPLETE        2
+
+#endif /* _LINUX_COMPACTION_H */
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 7a07b17d27c5..7238231b8dd4 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -19,6 +19,7 @@ extern int fail_migrate_page(struct address_space *,
                         struct page *, struct page *);
 
 extern int migrate_prep(void);
+extern int migrate_prep_local(void);
 extern int migrate_vmas(struct mm_struct *mm,
                 const nodemask_t *from, const nodemask_t *to,
                 unsigned long flags);
@@ -30,6 +31,7 @@ static inline int migrate_pages(struct list_head *l, new_page_t x,
                 unsigned long private, int offlining) { return -ENOSYS; }
 
 static inline int migrate_prep(void) { return -ENOSYS; }
+static inline int migrate_prep_local(void) { return -ENOSYS; }
 
 static inline int migrate_vmas(struct mm_struct *mm,
                 const nodemask_t *from, const nodemask_t *to,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 98ea5bab963e..963f908af9d0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -337,6 +337,7 @@ void put_page(struct page *page);
 void put_pages_list(struct list_head *pages);
 
 void split_page(struct page *page, unsigned int order);
+int split_free_page(struct page *page);
 
 /*
  * Compound pages have a destructor function.  Provide a
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 1e8ce148d058..b6b614364dd8 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -152,6 +152,7 @@ enum {
 };
 
 #define SWAP_CLUSTER_MAX 32
+#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
 
 #define SWAP_MAP_MAX    0x3e    /* Max duplication count, in first swap_map */
 #define SWAP_MAP_BAD    0x3f    /* Note pageblock is bad, in first swap_map */
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 117f0dd8ad03..b421d1b22b62 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -43,6 +43,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
                 KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
                 KSWAPD_SKIP_CONGESTION_WAIT,
                 PAGEOUTRUN, ALLOCSTALL, PGROTATED,
+#ifdef CONFIG_COMPACTION
+                COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
+#endif
 #ifdef CONFIG_HUGETLB_PAGE
                 HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
 #endif