[PATCH 07/14] zone_reclaim: remove /proc/sys/vm/zone_reclaim_interval

Christoph Lameter
2006-06-21T18:09:37Z

The zone_reclaim_interval was necessary because we were not able to determine
how many unmapped pages exist in a zone. Therefore we had to scan in
intervals to figure out if any pages were unmapped.

With the zoned counters and NR_ANON_PAGES we now know the number of pagecache pages
and the number of mapped pages in a zone. So we can simply skip the reclaim
if there is an insufficient number of unmapped pages. We use SWAP_CLUSTER_MAX
as the boundary.

Drop all support for /proc/sys/vm/zone_reclaim_interval.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

Index: linux-2.6.17-mm1/include/linux/mmzone.h
===================================================================
--- linux-2.6.17-mm1.orig/include/linux/mmzone.h 2006-06-21 07:37:46.333038070 -0700
+++ linux-2.6.17-mm1/include/linux/mmzone.h 2006-06-21 07:38:54.090553468 -0700
@@ -179,12 +179,6 @@ struct zone {

/* Zone statistics */
atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
- /*
- * timestamp (in jiffies) of the last zone reclaim that did not
- * result in freeing of pages. This is used to avoid repeated scans
- * if all memory in the zone is in use.
- */
- unsigned long last_unsuccessful_zone_reclaim;

/*
* prev_priority holds the scanning priority for this zone. It is
Index: linux-2.6.17-mm1/include/linux/swap.h
===================================================================
--- linux-2.6.17-mm1.orig/include/linux/swap.h 2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17-mm1/include/linux/swap.h 2006-06-21 07:38:54.091529970 -0700
@@ -194,7 +194,6 @@ extern pageout_t pageout(struct page *pa

#ifdef CONFIG_NUMA
extern int zone_reclaim_mode;
-extern int zone_reclaim_interval;
extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
#else
#define zone_reclaim_mode 0
Index: linux-2.6.17-mm1/kernel/sysctl.c
===================================================================
--- linux-2.6.17-mm1.orig/kernel/sysctl.c 2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17-mm1/kernel/sysctl.c 2006-06-21 07:38:54.094459475 -0700
@@ -905,15 +905,6 @@ static ctl_table vm_table[] = {
.strategy = &sysctl_intvec,
.extra1 = &zero,
},
- {
- .ctl_name = VM_ZONE_RECLAIM_INTERVAL,
- .procname = "zone_reclaim_interval",
- .data = &zone_reclaim_interval,
- .maxlen = sizeof(zone_reclaim_interval),
- .mode = 0644,
- .proc_handler = &proc_dointvec_jiffies,
- .strategy = &sysctl_jiffies,
- },
#endif
{ .ctl_name = 0 }
};
Index: linux-2.6.17-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.17-mm1.orig/mm/vmscan.c 2006-06-21 07:38:28.451518977 -0700
+++ linux-2.6.17-mm1/mm/vmscan.c 2006-06-21 07:38:54.095435977 -0700
@@ -1384,11 +1384,6 @@ int zone_reclaim_mode __read_mostly;
#define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */

/*
- * Mininum time between zone reclaim scans
- */
-int zone_reclaim_interval __read_mostly = 30*HZ;
-
-/*
* Priority for ZONE_RECLAIM. This determines the fraction of pages
* of a node considered for each zone_reclaim. 4 scans 1/16th of
* a zone.
@@ -1452,16 +1447,6 @@ static int __zone_reclaim(struct zone *z

p->reclaim_state = NULL;
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
-
- if (nr_reclaimed == 0) {
- /*
- * We were unable to reclaim enough pages to stay on node. We
- * now allow off node accesses for a certain time period before
- * trying again to reclaim pages from the local zone.
- */
- zone->last_unsuccessful_zone_reclaim = jiffies;
- }
-
return nr_reclaimed >= nr_pages;
}

@@ -1471,13 +1456,17 @@ int zone_reclaim(struct zone *zone, gfp_
int node_id;

/*
- * Do not reclaim if there was a recent unsuccessful attempt at zone
- * reclaim. In that case we let allocations go off node for the
- * zone_reclaim_interval. Otherwise we would scan for each off-node
- * page allocation.
+ * Do not reclaim if there are not enough reclaimable pages in this
+ * zone that would satify this allocations.
+ *
+ * All unmapped pagecache pages are reclaimable.
+ *
+ * Both counters may be temporarily off a bit so we use
+ * SWAP_CLUSTER_MAX as the boundary. It may also be good to
+ * leave a few frequently used unmapped pagecache pages around.
*/
- if (time_before(jiffies,
- zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
+ if (zone_page_state(zone, NR_FILE_PAGES) -
+ zone_page_state(zone, NR_FILE_MAPPED) < SWAP_CLUSTER_MAX)
return 0;

/*
Index: linux-2.6.17-mm1/Documentation/sysctl/vm.txt
===================================================================
--- linux-2.6.17-mm1.orig/Documentation/sysctl/vm.txt 2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17-mm1/Documentation/sysctl/vm.txt 2006-06-21 07:39:34.186698961 -0700
@@ -28,7 +28,6 @@ Currently, these files are in /proc/sys/
- block_dump
- drop-caches
- zone_reclaim_mode
-- zone_reclaim_interval

==============================================================

@@ -166,15 +165,3 @@ use of files and builds up large slab ca
shrink operation is global, may take a long time and free slabs
in all nodes of the system.

-================================================================
-
-zone_reclaim_interval:
-
-The time allowed for off node allocations after zone reclaim
-has failed to reclaim enough pages to allow a local allocation.
-
-Time is set in seconds and set by default to 30 seconds.
-
-Reduce the interval if undesired off node allocations occur. However, too
-frequent scans will have a negative impact onoff node allocation performance.
-