/* * 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> static LIST_HEAD(percpu_counters); static DEFINE_MUTEX(percpu_counters_lock); void percpu_counter_set(struct percpu_counter *fbc, s64 amount) { int cpu; spin_lock(&fbc->lock); for_each_possible_cpu(cpu) { s32 *pcount = per_cpu_ptr(fbc->counters, cpu); *pcount = 0; } fbc->count = amount; spin_unlock(&fbc->lock); } EXPORT_SYMBOL(percpu_counter_set); void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) { s64 count; s32 *pcount; int cpu = get_cpu(); pcount = per_cpu_ptr(fbc->counters, cpu); count = *pcount + amount; if (count >= batch || count <= -batch) { spin_lock(&fbc->lock); fbc->count += count; *pcount = 0; spin_unlock(&fbc->lock); } else { *pcount = count; } put_cpu(); } EXPORT_SYMBOL(__percpu_counter_add); /* * 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; } EXPORT_SYMBOL(__percpu_counter_sum); int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, struct lock_class_key *key) { spin_lock_init(&fbc->lock); lockdep_set_class(&fbc->lock, key); fbc->count = amount; fbc->counters = alloc_percpu(s32); if (!fbc->counters) return -ENOMEM; #ifdef CONFIG_HOTPLUG_CPU mutex_lock(&percpu_counters_lock); list_add(&fbc->list, &percpu_counters); mutex_unlock(&percpu_counters_lock); #endif return 0; } EXPORT_SYMBOL(__percpu_counter_init); void percpu_counter_destroy(struct percpu_counter *fbc) { if (!fbc->counters) return; #ifdef CONFIG_HOTPLUG_CPU mutex_lock(&percpu_counters_lock); list_del(&fbc->list); mutex_unlock(&percpu_counters_lock); #endif free_percpu(fbc->counters); fbc->counters = NULL; } EXPORT_SYMBOL(percpu_counter_destroy); int percpu_counter_batch __read_mostly = 32; EXPORT_SYMBOL(percpu_counter_batch); static void compute_batch_value(void) { int nr = num_online_cpus(); percpu_counter_batch = max(32, nr*2); } static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu) { #ifdef CONFIG_HOTPLUG_CPU unsigned int cpu; struct percpu_counter *fbc; compute_batch_value(); 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; unsigned long flags; spin_lock_irqsave(&fbc->lock, flags); pcount = per_cpu_ptr(fbc->counters, cpu); fbc->count += *pcount; *pcount = 0; spin_unlock_irqrestore(&fbc->lock, flags); } mutex_unlock(&percpu_counters_lock); #endif return NOTIFY_OK; } /* * Compare counter against given value. * Return 1 if greater, 0 if equal and -1 if less */ int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) { s64 count; count = percpu_counter_read(fbc); /* Check to see if rough count will be sufficient for comparison */ if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) { if (count > rhs) return 1; else return -1; } /* Need to use precise count */ count = percpu_counter_sum(fbc); if (count > rhs) return 1; else if (count < rhs) return -1; else return 0; } EXPORT_SYMBOL(percpu_counter_compare); static int __init percpu_counter_startup(void) { compute_batch_value(); hotcpu_notifier(percpu_counter_hotcpu_callback, 0); return 0; } module_init(percpu_counter_startup);