diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
new file mode 100644
index 0000000..7a87003
--- /dev/null
+++ b/lib/percpu_counter.c
@@ -0,0 +1,46 @@
+/*
+ * Fast batching percpu counters.
+ */
+
+#include <linux/percpu_counter.h>
+#include <linux/module.h>
+
+void percpu_counter_mod(struct percpu_counter *fbc, long amount)
+{
+	long count;
+	long *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()
+ */
+long percpu_counter_sum(struct percpu_counter *fbc)
+{
+	long ret;
+	int cpu;
+
+	spin_lock(&fbc->lock);
+	ret = fbc->count;
+	for_each_possible_cpu(cpu) {
+		long *pcount = per_cpu_ptr(fbc->counters, cpu);
+		ret += *pcount;
+	}
+	spin_unlock(&fbc->lock);
+	return ret < 0 ? 0 : ret;
+}
+EXPORT_SYMBOL(percpu_counter_sum);