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/*
* linux/mm/vmstat.c
*
* Manages VM statistics
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*
* zoned VM statistics
* Copyright (C) 2006 Silicon Graphics, Inc.,
* Christoph Lameter <christoph@lameter.com>
*/
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/vmstat.h>
#include <linux/sched.h>
#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
EXPORT_PER_CPU_SYMBOL(vm_event_states);
static void sum_vm_events(unsigned long *ret, cpumask_t *cpumask)
{
int cpu;
int i;
memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));
for_each_cpu_mask_nr(cpu, *cpumask) {
struct vm_event_state *this = &per_cpu(vm_event_states, cpu);
for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
ret[i] += this->event[i];
}
}
/*
* Accumulate the vm event counters across all CPUs.
* The result is unavoidably approximate - it can change
* during and after execution of this function.
*/
void all_vm_events(unsigned long *ret)
{
get_online_cpus();
sum_vm_events(ret, &cpu_online_map);
put_online_cpus();
}
EXPORT_SYMBOL_GPL(all_vm_events);
#ifdef CONFIG_HOTPLUG
/*
* Fold the foreign cpu events into our own.
*
* This is adding to the events on one processor
* but keeps the global counts constant.
*/
void vm_events_fold_cpu(int cpu)
{
struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu);
int i;
for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
count_vm_events(i, fold_state->event[i]);
fold_state->event[i] = 0;
}
}
#endif /* CONFIG_HOTPLUG */
#endif /* CONFIG_VM_EVENT_COUNTERS */
/*
* Manage combined zone based / global counters
*
* vm_stat contains the global counters
*/
atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
EXPORT_SYMBOL(vm_stat);
#ifdef CONFIG_SMP
static int calculate_threshold(struct zone *zone)
{
int threshold;
int mem; /* memory in 128 MB units */
/*
* The threshold scales with the number of processors and the amount
* of memory per zone. More memory means that we can defer updates for
* longer, more processors could lead to more contention.
* fls() is used to have a cheap way of logarithmic scaling.
*
* Some sample thresholds:
*
* Threshold Processors (fls) Zonesize fls(mem+1)
* ------------------------------------------------------------------
* 8 1 1 0.9-1 GB 4
* 16 2 2 0.9-1 GB 4
* 20 2 2 1-2 GB 5
* 24 2 2 2-4 GB 6
* 28 2 2 4-8 GB 7
* 32 2 2 8-16 GB 8
* 4 2 2 <128M 1
* 30 4 3 2-4 GB 5
* 48 4 3 8-16 GB 8
* 32 8 4 1-2 GB 4
* 32 8 4 0.9-1GB 4
* 10 16 5 <128M 1
* 40 16 5 900M 4
* 70 64 7 2-4 GB 5
* 84 64 7 4-8 GB 6
* 108 512 9 4-8 GB 6
* 125 1024 10 8-16 GB 8
* 125 1024 10 16-32 GB 9
*/
mem = zone->present_pages >> (27 - PAGE_SHIFT);
threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem));
/*
* Maximum threshold is 125
*/
threshold = min(125, threshold);
return threshold;
}
/*
* Refresh the thresholds for each zone.
*/
static void refresh_zone_stat_thresholds(void)
{
struct zone *zone;
int cpu;
int threshold;
for_each_zone(zone) {
if (!zone->present_pages)
continue;
threshold = calculate_threshold(zone);
for_each_online_cpu(cpu)
zone_pcp(zone, cpu)->stat_threshold = threshold;
}
}
/*
* For use when we know that interrupts are disabled.
*/
void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
int delta)
{
struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
s8 *p = pcp->vm_stat_diff + item;
long x;
x = delta + *p;
if (unlikely(x > pcp->stat_threshold || x < -pcp->stat_threshold)) {
zone_page_state_add(x, zone, item);
x = 0;
}
*p = x;
}
EXPORT_SYMBOL(__mod_zone_page_state);
/*
* For an unknown interrupt state
*/
void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
int delta)
{
unsigned long flags;
local_irq_save(flags);
__mod_zone_page_state(zone, item, delta);
local_irq_restore(flags);
}
EXPORT_SYMBOL(mod_zone_page_state);
/*
* Optimized increment and decrement functions.
*
* These are only for a single page and therefore can take a struct page *
* argument instead of struct zone *. This allows the inclusion of the code
* generated for page_zone(page) into the optimized functions.
*
* No overflow check is necessary and therefore the differential can be
* incremented or decremented in place which may allow the compilers to
* generate better code.
* The increment or decrement is known and therefore one boundary check can
* be omitted.
*
* NOTE: These functions are very performance sensitive. Change only
* with care.
*
* Some processors have inc/dec instructions that are atomic vs an interrupt.
* However, the code must first determine the differential location in a zone
* based on the processor number and then inc/dec the counter. There is no
* guarantee without disabling preemption that the processor will not change
* in between and therefore the atomicity vs. interrupt cannot be exploited
* in a useful way here.
*/
void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
{
struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
s8 *p = pcp->vm_stat_diff + item;
(*p)++;
if (unlikely(*p > pcp->stat_threshold)) {
int overstep = pcp->stat_threshold / 2;
zone_page_state_add(*p + overstep, zone, item);
*p = -overstep;
}
}
void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
{
__inc_zone_state(page_zone(page), item);
}
EXPORT_SYMBOL(__inc_zone_page_state
|