mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 16:29:59 +00:00
![Andrew Morton](/assets/img/avatar_default.png)
Now that we have implemented hotunplug-time counter spilling, percpu_counter_sum() only needs to look at online CPUs. Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
112 lines
2.4 KiB
C
112 lines
2.4 KiB
C
/*
|
|
* Fast batching percpu counters.
|
|
*/
|
|
|
|
#include <linux/percpu_counter.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/init.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/module.h>
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static LIST_HEAD(percpu_counters);
|
|
static DEFINE_MUTEX(percpu_counters_lock);
|
|
#endif
|
|
|
|
void percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
|
|
{
|
|
long count;
|
|
s32 *pcount;
|
|
int cpu = get_cpu();
|
|
|
|
pcount = per_cpu_ptr(fbc->counters, cpu);
|
|
count = *pcount + amount;
|
|
if (count >= FBC_BATCH || count <= -FBC_BATCH) {
|
|
spin_lock(&fbc->lock);
|
|
fbc->count += count;
|
|
*pcount = 0;
|
|
spin_unlock(&fbc->lock);
|
|
} else {
|
|
*pcount = count;
|
|
}
|
|
put_cpu();
|
|
}
|
|
EXPORT_SYMBOL(percpu_counter_mod);
|
|
|
|
/*
|
|
* Add up all the per-cpu counts, return the result. This is a more accurate
|
|
* but much slower version of percpu_counter_read_positive()
|
|
*/
|
|
s64 percpu_counter_sum(struct percpu_counter *fbc)
|
|
{
|
|
s64 ret;
|
|
int cpu;
|
|
|
|
spin_lock(&fbc->lock);
|
|
ret = fbc->count;
|
|
for_each_online_cpu(cpu) {
|
|
s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
|
|
ret += *pcount;
|
|
}
|
|
spin_unlock(&fbc->lock);
|
|
return ret < 0 ? 0 : ret;
|
|
}
|
|
EXPORT_SYMBOL(percpu_counter_sum);
|
|
|
|
void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
|
|
{
|
|
spin_lock_init(&fbc->lock);
|
|
fbc->count = amount;
|
|
fbc->counters = alloc_percpu(s32);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
mutex_lock(&percpu_counters_lock);
|
|
list_add(&fbc->list, &percpu_counters);
|
|
mutex_unlock(&percpu_counters_lock);
|
|
#endif
|
|
}
|
|
EXPORT_SYMBOL(percpu_counter_init);
|
|
|
|
void percpu_counter_destroy(struct percpu_counter *fbc)
|
|
{
|
|
free_percpu(fbc->counters);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
mutex_lock(&percpu_counters_lock);
|
|
list_del(&fbc->list);
|
|
mutex_unlock(&percpu_counters_lock);
|
|
#endif
|
|
}
|
|
EXPORT_SYMBOL(percpu_counter_destroy);
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
unsigned int cpu;
|
|
struct percpu_counter *fbc;
|
|
|
|
if (action != CPU_DEAD)
|
|
return NOTIFY_OK;
|
|
|
|
cpu = (unsigned long)hcpu;
|
|
mutex_lock(&percpu_counters_lock);
|
|
list_for_each_entry(fbc, &percpu_counters, list) {
|
|
s32 *pcount;
|
|
|
|
spin_lock(&fbc->lock);
|
|
pcount = per_cpu_ptr(fbc->counters, cpu);
|
|
fbc->count += *pcount;
|
|
*pcount = 0;
|
|
spin_unlock(&fbc->lock);
|
|
}
|
|
mutex_unlock(&percpu_counters_lock);
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static int __init percpu_counter_startup(void)
|
|
{
|
|
hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
|
|
return 0;
|
|
}
|
|
module_init(percpu_counter_startup);
|
|
#endif
|