From c67ad917cbf21b2862e2cf8e8b28339872ef7927 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Sun, 15 Jul 2007 23:39:51 -0700 Subject: percpu_counters(): use cpu notifiers per-cpu counters presently must iterate over all possible CPUs in the exhaustive percpu_counter_sum(). But it can be much better to only iterate over the presently-online CPUs. To do this, we must arrange for an offlined CPU's count to be spilled into the counter's central count. We can do this for all percpu_counters in the machine by linking them into a single global list and walking that list at CPU_DEAD time. (I hope. Might have race windows in which the percpu_counter_sum() count is inaccurate?) Cc: Gautham R Shenoy Cc: Oleg Nesterov Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/percpu_counter.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) (limited to 'lib') diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 850449080e1..8901c4e9c2e 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -3,8 +3,17 @@ */ #include +#include +#include +#include +#include #include +#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; @@ -44,3 +53,60 @@ s64 percpu_counter_sum(struct percpu_counter *fbc) 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 -- cgit v1.2.3