mm: compaction: add /proc trigger for memory compaction

Add a proc file /proc/sys/vm/compact_memory.  When an arbitrary value is
written to the file, all zones are compacted.  The expected user of such a
trigger is a job scheduler that prepares the system before the target
application runs.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4c93486b45d1..284f330d6a01 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -37,6 +37,7 @@
 #include <linux/highuid.h>
 #include <linux/writeback.h>
 #include <linux/ratelimit.h>
+#include <linux/compaction.h>
 #include <linux/hugetlb.h>
 #include <linux/initrd.h>
 #include <linux/key.h>
@@ -1121,6 +1122,15 @@ static struct ctl_table vm_table[] = {
                 .mode           = 0644,
                 .proc_handler   = drop_caches_sysctl_handler,
         },
+#ifdef CONFIG_COMPACTION
+        {
+                .procname       = "compact_memory",
+                .data           = &sysctl_compact_memory,
+                .maxlen         = sizeof(int),
+                .mode           = 0200,
+                .proc_handler   = sysctl_compaction_handler,
+        },
+#endif /* CONFIG_COMPACTION */
         {
                 .procname       = "min_free_kbytes",
                 .data           = &min_free_kbytes,