[PATCH] percpu_counter_sum()
Implement percpu_counter_sum(). This is a more accurate but slower version of
percpu_counter_read_positive().
We need this for Alex's speedup-ext3_statfs patch and for the nr_file
accounting fix. Otherwise these things would be too inaccurate on large CPU
counts.
Cc: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
index bd6708e..6825255 100644
--- a/include/linux/percpu_counter.h
+++ b/include/linux/percpu_counter.h
@@ -39,6 +39,7 @@
}
void percpu_counter_mod(struct percpu_counter *fbc, long amount);
+long percpu_counter_sum(struct percpu_counter *fbc);
static inline long percpu_counter_read(struct percpu_counter *fbc)
{
@@ -92,6 +93,11 @@
return fbc->count;
}
+static inline long percpu_counter_sum(struct percpu_counter *fbc)
+{
+ return percpu_counter_read_positive(fbc);
+}
+
#endif /* CONFIG_SMP */
static inline void percpu_counter_inc(struct percpu_counter *fbc)
diff --git a/mm/swap.c b/mm/swap.c
index cce3dda..e9ec06d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -489,13 +489,34 @@
if (count >= FBC_BATCH || count <= -FBC_BATCH) {
spin_lock(&fbc->lock);
fbc->count += count;
+ *pcount = 0;
spin_unlock(&fbc->lock);
- count = 0;
+ } else {
+ *pcount = count;
}
- *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_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);
#endif
/*