[PATCH 1/4] vmscan: change the number of the unmapped files in zone reclaim

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Subject: [PATCH] vmscan: change the number of the unmapped files in zone reclaim

Documentation/sysctl/vm.txt says

	A percentage of the total pages in each zone.  Zone reclaim will only
	occur if more than this percentage of pages are file backed and unmapped.
	This is to insure that a minimal amount of local pages is still available for
	file I/O even if the node is overallocated.

However, zone_page_state(zone, NR_FILE_PAGES) contain some non file backed pages
(e.g. swapcache, buffer-head)

The right calculation is to use NR_{IN}ACTIVE_FILE.


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
---
 mm/vmscan.c |   21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

Index: b/mm/vmscan.c
===================================================================
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2397,6 +2397,7 @@ static int __zone_reclaim(struct zone *z
 		.isolate_pages = isolate_pages_global,
 	};
 	unsigned long slab_reclaimable;
+	long nr_unmapped_file_pages;
 
 	disable_swap_token();
 	cond_resched();
@@ -2409,9 +2410,11 @@ static int __zone_reclaim(struct zone *z
 	reclaim_state.reclaimed_slab = 0;
 	p->reclaim_state = &reclaim_state;
 
-	if (zone_page_state(zone, NR_FILE_PAGES) -
-		zone_page_state(zone, NR_FILE_MAPPED) >
-		zone->min_unmapped_pages) {
+	nr_unmapped_file_pages = zone_page_state(zone, NR_INACTIVE_FILE) +
+				 zone_page_state(zone, NR_ACTIVE_FILE) -
+				 zone_page_state(zone, NR_FILE_MAPPED);
+
+	if (nr_unmapped_file_pages > zone->min_unmapped_pages) {
 		/*
 		 * Free memory by calling shrink zone with increasing
 		 * priorities until we have enough memory freed.
@@ -2458,6 +2461,8 @@ int zone_reclaim(struct zone *zone, gfp_
 {
 	int node_id;
 	int ret;
+	long nr_unmapped_file_pages;
+	long nr_slab_reclaimable;
 
 	/*
 	 * Zone reclaim reclaims unmapped file backed pages and
@@ -2469,10 +2474,12 @@ int zone_reclaim(struct zone *zone, gfp_
 	 * if less than a specified percentage of the zone is used by
 	 * unmapped file backed pages.
 	 */
-	if (zone_page_state(zone, NR_FILE_PAGES) -
-	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
-	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
-			<= zone->min_slab_pages)
+	nr_unmapped_file_pages = zone_page_state(zone, NR_INACTIVE_FILE) +
+				 zone_page_state(zone, NR_ACTIVE_FILE) -
+				 zone_page_state(zone, NR_FILE_MAPPED);
+	nr_slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
+	if (nr_unmapped_file_pages <= zone->min_unmapped_pages &&
+	    nr_slab_reclaimable <= zone->min_slab_pages)
 		return 0;
 
 	if (zone_is_all_unreclaimable(zone))


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