Subject: + vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats.patch added to -mm tree
To: cl@xxxxxxxxx,adobriyan@xxxxxxxxx,js1304@xxxxxxxxx,kosaki.motohiro@xxxxxxxxxxxxxx,tj@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 07 Aug 2013 13:43:10 -0700
The patch titled
Subject: vmstat: use this_cpu() to avoid irqon/off sequence in refresh_cpu_vm_stats
has been added to the -mm tree. Its filename is
vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats.patch
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------------------------------------------------------
From: Christoph Lameter <cl@xxxxxxxxx>
Subject: vmstat: use this_cpu() to avoid irqon/off sequence in refresh_cpu_vm_stats
Disabling interrupts repeatedly can be avoided in the inner loop if we use
a this_cpu operation.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmstat.c | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)
diff -puN mm/vmstat.c~vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats mm/vmstat.c
--- a/mm/vmstat.c~vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats
+++ a/mm/vmstat.c
@@ -437,33 +437,29 @@ static inline void fold_diff(int *diff)
* with the global counters. These could cause remote node cache line
* bouncing and will have to be only done when necessary.
*/
-static void refresh_cpu_vm_stats(int cpu)
+static void refresh_cpu_vm_stats(void)
{
struct zone *zone;
int i;
int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
for_each_populated_zone(zone) {
- struct per_cpu_pageset *p;
+ struct per_cpu_pageset __percpu *p = zone->pageset;
- p = per_cpu_ptr(zone->pageset, cpu);
+ for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
+ int v;
- for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
- if (p->vm_stat_diff[i]) {
- unsigned long flags;
- int v;
+ v = this_cpu_xchg(p->vm_stat_diff[i], 0);
+ if (v) {
- local_irq_save(flags);
- v = p->vm_stat_diff[i];
- p->vm_stat_diff[i] = 0;
- local_irq_restore(flags);
atomic_long_add(v, &zone->vm_stat[i]);
global_diff[i] += v;
#ifdef CONFIG_NUMA
/* 3 seconds idle till flush */
- p->expire = 3;
+ __this_cpu_write(p->expire, 3);
#endif
}
+ }
cond_resched();
#ifdef CONFIG_NUMA
/*
@@ -473,23 +469,24 @@ static void refresh_cpu_vm_stats(int cpu
* Check if there are pages remaining in this pageset
* if not then there is nothing to expire.
*/
- if (!p->expire || !p->pcp.count)
+ if (!__this_cpu_read(p->expire) ||
+ !__this_cpu_read(p->pcp.count))
continue;
/*
* We never drain zones local to this processor.
*/
if (zone_to_nid(zone) == numa_node_id()) {
- p->expire = 0;
+ __this_cpu_write(p->expire, 0);
continue;
}
- p->expire--;
- if (p->expire)
+
+ if (__this_cpu_dec_return(p->expire))
continue;
- if (p->pcp.count)
- drain_zone_pages(zone, &p->pcp);
+ if (__this_cpu_read(p->pcp.count))
+ drain_zone_pages(zone, __this_cpu_ptr(&p->pcp));
#endif
}
fold_diff(global_diff);
@@ -1215,7 +1212,7 @@ int sysctl_stat_interval __read_mostly =
static void vmstat_update(struct work_struct *w)
{
- refresh_cpu_vm_stats(smp_processor_id());
+ refresh_cpu_vm_stats();
schedule_delayed_work(&__get_cpu_var(vmstat_work),
round_jiffies_relative(sysctl_stat_interval));
}
_
Patches currently in -mm which might be from cl@xxxxxxxxx are
vmstat-create-separate-function-to-fold-per-cpu-diffs-into-local-counters.patch
vmstat-create-fold_diff.patch
vmstat-use-this_cpu-to-avoid-irqon-off-sequence-in-refresh_cpu_vm_stats.patch
linux-next.patch
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