percpu_counter_sum_positive() will provide more accurate info.
As with percpu_counter_read_positive(), in worst case the deviation
could be 'batch * nr_cpus', which is totalram_pages/256 for now,
and will be more when the batch gets enlarged.
Its time cost is about 800 nanoseconds on a 2C/4T platform and
2~3 microseconds on a 2S/36C/72T server in normal case, and in
worst case where vm_committed_as's spinlock is under severe
contention, it costs 30~40 microseconds for the 2S/36C/72T sever,
which should be fine for its only two users: /proc/meminfo and
HyperV balloon driver's status trace per second.
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
---
mm/util.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/util.c b/mm/util.c
index 988d11e..3de78e9 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -774,7 +774,7 @@ struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
*/
unsigned long vm_memory_committed(void)
{
- return percpu_counter_read_positive(&vm_committed_as);
+ return percpu_counter_sum_positive(&vm_committed_as);
}
EXPORT_SYMBOL_GPL(vm_memory_committed);
--
2.7.4
