---
Documentation/sysctl/vm.txt | 19 +++++++++++++++++++
include/linux/sysctl.h | 1 +
kernel/sysctl.c | 13 ++++++++++++-
mm/vmstat.c | 4 +++-
4 files changed, 35 insertions(+), 2 deletions(-)
Index: slub/Documentation/sysctl/vm.txt
===================================================================
--- slub.orig/Documentation/sysctl/vm.txt 2007-04-30 20:20:19.000000000 -0700
+++ slub/Documentation/sysctl/vm.txt 2007-04-30 20:56:18.000000000 -0700
@@ -34,6 +34,7 @@ Currently, these files are in /proc/sys/
- swap_prefetch
- readahead_ratio
- readahead_hit_rate
+- stat_interval
==============================================================
@@ -275,3 +276,21 @@ Possible values can be:
The larger value, the more capabilities, with more possible overheads.
The default value is 1.
+
+================================================================
+
+stat_interval
+
+The period (seconds) in which the vm statistics are consolidated if the
+kernel supports SMP. Differentials to VM statistics are kept in per cpu
+fields and are only consolidated with per zone and global counters if the
+differentials cross certain limits. This limits the frequency of global
+updates and results in good scaling of the VM counters. However, if those
+counters are below the limits then the global and per zone counters are
+off by that value. So we should consolidate the counters at some point.
+So the kernel runs a statistics update at regular intervals to consolidate
+the per cpu differentials that are below the update limits. The interval
+determines the frequency of these consolidations.
+
+The default value is 1 second.
+
Index: slub/include/linux/sysctl.h
===================================================================
--- slub.orig/include/linux/sysctl.h 2007-04-30 20:03:21.000000000 -0700
+++ slub/include/linux/sysctl.h 2007-04-30 20:31:13.000000000 -0700
@@ -208,6 +208,7 @@ enum
VM_VDSO_ENABLED=34, /* map VDSO into new processes? */
VM_MIN_SLAB=35, /* Percent pages ignored by zone reclaim */
VM_HUGETLB_TREAT_MOVABLE=36, /* Allocate hugepages from ZONE_MOVABLE */
+ VM_STAT_INTERVAL=37, /* Statistics timer */
/* s390 vm cmm sysctls */
VM_CMM_PAGES=1111,
Index: slub/kernel/sysctl.c
===================================================================
--- slub.orig/kernel/sysctl.c 2007-04-30 20:04:55.000000000 -0700
+++ slub/kernel/sysctl.c 2007-04-30 20:50:03.000000000 -0700
@@ -80,7 +80,7 @@ extern int sysctl_drop_caches;
extern int percpu_pagelist_fraction;
extern int compat_log;
extern int maps_protect;
-
+extern int sysctl_stat_interval;
#if defined(CONFIG_ADAPTIVE_READAHEAD)
extern int readahead_ratio;
extern int readahead_hit_rate;
@@ -894,6 +894,17 @@ static ctl_table vm_table[] = {
.extra2 = &one_hundred,
},
#endif
+#ifdef CONFIG_SMP
+ {
+ .ctl_name = VM_STAT_INTERVAL,
+ .procname = "stat_interval",
+ .data = &sysctl_stat_interval,
+ .maxlen = sizeof(sysctl_stat_interval),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_jiffies,
+ .strategy = &sysctl_jiffies,
+ },
+#endif
#if defined(CONFIG_X86_32) || \
(defined(CONFIG_SUPERH) && defined(CONFIG_VSYSCALL))
{
Index: slub/mm/vmstat.c
===================================================================
--- slub.orig/mm/vmstat.c 2007-04-30 20:16:18.000000000 -0700
+++ slub/mm/vmstat.c 2007-04-30 20:51:06.000000000 -0700
@@ -685,11 +685,13 @@ const struct seq_operations vmstat_op =
#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct delayed_work, vmstat_work);
+int sysctl_stat_interval __read_mostly = HZ;
static void vmstat_update(struct work_struct *w)
{
refresh_cpu_vm_stats(smp_processor_id());
- schedule_delayed_work(&__get_cpu_var(vmstat_work), HZ);
+ schedule_delayed_work(&__get_cpu_var(vmstat_work),
+ sysctl_stat_interval);
}
static void __devinit start_cpu_timer(int cpu)