diff options
Diffstat (limited to 'lib/percpu_counter.c')
| -rw-r--r-- | lib/percpu_counter.c | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c new file mode 100644 index 000000000..f051d69f0 --- /dev/null +++ b/lib/percpu_counter.c @@ -0,0 +1,229 @@ +/* + * 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> +#include <linux/debugobjects.h> + +#ifdef CONFIG_HOTPLUG_CPU +static LIST_HEAD(percpu_counters); +static DEFINE_SPINLOCK(percpu_counters_lock); +#endif + +#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER + +static struct debug_obj_descr percpu_counter_debug_descr; + +static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state) +{ + struct percpu_counter *fbc = addr; + + switch (state) { + case ODEBUG_STATE_ACTIVE: + percpu_counter_destroy(fbc); + debug_object_free(fbc, &percpu_counter_debug_descr); + return 1; + default: + return 0; + } +} + +static struct debug_obj_descr percpu_counter_debug_descr = { + .name = "percpu_counter", + .fixup_free = percpu_counter_fixup_free, +}; + +static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) +{ + debug_object_init(fbc, &percpu_counter_debug_descr); + debug_object_activate(fbc, &percpu_counter_debug_descr); +} + +static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) +{ + debug_object_deactivate(fbc, &percpu_counter_debug_descr); + debug_object_free(fbc, &percpu_counter_debug_descr); +} + +#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ +static inline void debug_percpu_counter_activate(struct percpu_counter *fbc) +{ } +static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc) +{ } +#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ + +void percpu_counter_set(struct percpu_counter *fbc, s64 amount) +{ + int cpu; + unsigned long flags; + + raw_spin_lock_irqsave(&fbc->lock, flags); + for_each_possible_cpu(cpu) { + s32 *pcount = per_cpu_ptr(fbc->counters, cpu); + *pcount = 0; + } + fbc->count = amount; + raw_spin_unlock_irqrestore(&fbc->lock, flags); +} +EXPORT_SYMBOL(percpu_counter_set); + +void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) +{ + s64 count; + + preempt_disable(); + count = __this_cpu_read(*fbc->counters) + amount; + if (count >= batch || count <= -batch) { + unsigned long flags; + raw_spin_lock_irqsave(&fbc->lock, flags); + fbc->count += count; + __this_cpu_sub(*fbc->counters, count - amount); + raw_spin_unlock_irqrestore(&fbc->lock, flags); + } else { + this_cpu_add(*fbc->counters, amount); + } + preempt_enable(); +} +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; + unsigned long flags; + + raw_spin_lock_irqsave(&fbc->lock, flags); + ret = fbc->count; + for_each_online_cpu(cpu) { + s32 *pcount = per_cpu_ptr(fbc->counters, cpu); + ret += *pcount; + } + raw_spin_unlock_irqrestore(&fbc->lock, flags); + return ret; +} +EXPORT_SYMBOL(__percpu_counter_sum); + +int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp, + struct lock_class_key *key) +{ + unsigned long flags __maybe_unused; + + raw_spin_lock_init(&fbc->lock); + lockdep_set_class(&fbc->lock, key); + fbc->count = amount; + fbc->counters = alloc_percpu_gfp(s32, gfp); + if (!fbc->counters) + return -ENOMEM; + + debug_percpu_counter_activate(fbc); + +#ifdef CONFIG_HOTPLUG_CPU + INIT_LIST_HEAD(&fbc->list); + spin_lock_irqsave(&percpu_counters_lock, flags); + list_add(&fbc->list, &percpu_counters); + spin_unlock_irqrestore(&percpu_counters_lock, flags); +#endif + return 0; +} +EXPORT_SYMBOL(__percpu_counter_init); + +void percpu_counter_destroy(struct percpu_counter *fbc) +{ + unsigned long flags __maybe_unused; + + if (!fbc->counters) + return; + + debug_percpu_counter_deactivate(fbc); + +#ifdef CONFIG_HOTPLUG_CPU + spin_lock_irqsave(&percpu_counters_lock, flags); + list_del(&fbc->list); + spin_unlock_irqrestore(&percpu_counters_lock, flags); +#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 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 && action != CPU_DEAD_FROZEN) + return NOTIFY_OK; + + cpu = (unsigned long)hcpu; + spin_lock_irq(&percpu_counters_lock); + list_for_each_entry(fbc, &percpu_counters, list) { + s32 *pcount; + unsigned long flags; + + raw_spin_lock_irqsave(&fbc->lock, flags); + pcount = per_cpu_ptr(fbc->counters, cpu); + fbc->count += *pcount; + *pcount = 0; + raw_spin_unlock_irqrestore(&fbc->lock, flags); + } + spin_unlock_irq(&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, s32 batch) +{ + s64 count; + + count = percpu_counter_read(fbc); + /* Check to see if rough count will be sufficient for comparison */ + if (abs(count - rhs) > (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); |