[PATCH] percpu_counters: create lib/percpu_counter.c

- Move percpu_counter routines from mm/swap.c to lib/percpu_counter.c

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
new file mode 100644
index 000000000000..7a87003f8e8f
--- /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);