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Subject[PATCH 09/21] zone_reclaim: remove /proc/sys/vm/zone_reclaim_interval
Subject: zoned vm counters: use per zone counters to remove zone_reclaim_interval
From: Christoph Lameter <clameter@sgi.com>

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 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-rc6-cl/include/linux/mmzone.h
===================================================================
--- linux-2.6.17-rc6-cl.orig/include/linux/mmzone.h 2006-06-13 10:17:44.987532146 -0700
+++ linux-2.6.17-rc6-cl/include/linux/mmzone.h 2006-06-13 10:17:47.544991113 -0700
@@ -183,12 +183,6 @@ 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-rc6-cl/include/linux/swap.h
===================================================================
--- linux-2.6.17-rc6-cl.orig/include/linux/swap.h 2006-06-12 12:42:51.046775908 -0700
+++ linux-2.6.17-rc6-cl/include/linux/swap.h 2006-06-13 10:17:47.555732636 -0700
@@ -190,7 +190,6 @@ extern long vm_total_pages;

#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-rc6-cl/include/linux/sysctl.h
===================================================================
--- linux-2.6.17-rc6-cl.orig/include/linux/sysctl.h 2006-06-12 12:42:51.074117966 -0700
+++ linux-2.6.17-rc6-cl/include/linux/sysctl.h 2006-06-13 10:17:47.566474159 -0700
@@ -191,7 +191,6 @@ enum
VM_DROP_PAGECACHE=29, /* int: nuke lots of pagecache */
VM_PERCPU_PAGELIST_FRACTION=30,/* int: fraction of pages in each percpu_pagelist */
VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */
- VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
VM_PANIC_ON_OOM=33, /* panic at out-of-memory */
VM_VDSO_ENABLED=34, /* map VDSO into new processes? */
VM_SWAP_PREFETCH=35, /* swap prefetch */
Index: linux-2.6.17-rc6-cl/kernel/sysctl.c
===================================================================
--- linux-2.6.17-rc6-cl.orig/kernel/sysctl.c 2006-06-12 12:42:51.948087320 -0700
+++ linux-2.6.17-rc6-cl/kernel/sysctl.c 2006-06-13 10:17:47.586980703 -0700
@@ -1015,15 +1015,6 @@ 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
#ifdef CONFIG_X86_32
{
Index: linux-2.6.17-rc6-cl/mm/vmscan.c
===================================================================
--- linux-2.6.17-rc6-cl.orig/mm/vmscan.c 2006-06-13 10:17:44.989485150 -0700
+++ linux-2.6.17-rc6-cl/mm/vmscan.c 2006-06-13 10:17:47.588933707 -0700
@@ -1529,11 +1529,6 @@ 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.
@@ -1598,16 +1593,6 @@ 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;
}

@@ -1617,13 +1602,17 @@ 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_PAGECACHE) -
+ zone_page_state(zone, NR_MAPPED) < SWAP_CLUSTER_MAX)
return 0;

/*
Index: linux-2.6.17-rc6-cl/Documentation/sysctl/vm.txt
===================================================================
--- linux-2.6.17-rc6-cl.orig/Documentation/sysctl/vm.txt 2006-06-12 12:42:42.519959822 -0700
+++ linux-2.6.17-rc6-cl/Documentation/sysctl/vm.txt 2006-06-13 10:17:47.614322761 -0700
@@ -28,7 +28,6 @@ Currently, these files are in /proc/sys/
- block_dump
- drop-caches
- zone_reclaim_mode
-- zone_reclaim_interval
- panic_on_oom
- swap_prefetch
- readahead_ratio
@@ -172,18 +171,6 @@ 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.
-
-=============================================================
-
panic_on_oom

This enables or disables panic on out-of-memory feature. If this is set to 1,
-
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