initial_commit

1 files changed, 220 insertions, 0 deletions

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
new file mode 100644
index 00000000..28f2c33c
--- /dev/null
+++ b/lib/percpu_counter.c
@@ -0,0 +1,220 @@
+/*
+ * 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>
+
+static LIST_HEAD(percpu_counters);
+static DEFINE_MUTEX(percpu_counters_lock);
+
+#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;
+
+	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;
+
+	preempt_disable();
+	count = __this_cpu_read(*fbc->counters) + amount;
+	if (count >= batch || count <= -batch) {
+		spin_lock(&fbc->lock);
+		fbc->count += count;
+		__this_cpu_write(*fbc->counters, 0);
+		spin_unlock(&fbc->lock);
+	} else {
+		__this_cpu_write(*fbc->counters, count);
+	}
+	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;
+
+	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;
+
+	debug_percpu_counter_activate(fbc);
+
+#ifdef CONFIG_HOTPLUG_CPU
+	INIT_LIST_HEAD(&fbc->list);
+	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;
+
+	debug_percpu_counter_deactivate(fbc);
+
+#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);