[PATCH] vm: add per-zone writeout counter

The VM is supposed to minimise the number of pages which get written off the
LRU (for IO scheduling efficiency, and for high reclaim-success rates).  But
we don't actually have a clear way of showing how true this is.

So add `nr_vmscan_write' to /proc/vmstat and /proc/zoneinfo - the number of
pages which have been written by the vm scanner in this zone and globally.

Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 3 insertions, 1 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 87779dda4ec6..87d340999ce8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -19,6 +19,7 @@
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/vmstat.h>
 #include <linux/file.h>
 #include <linux/writeback.h>
 #include <linux/blkdev.h>
@@ -370,7 +371,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
                         /* synchronous write or broken a_ops? */
                         ClearPageReclaim(page);
                 }
-
+                inc_zone_page_state(page, NR_VMSCAN_WRITE);
                 return PAGE_SUCCESS;
         }
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 490d8c1a0ded..69c657132e1f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -465,6 +465,7 @@ static char *vmstat_text[] = {
         "nr_writeback",
         "nr_unstable",
         "nr_bounce",
+        "nr_vmscan_write",
 
 #ifdef CONFIG_NUMA
         "numa_hit",