From: Florian-Ewald Mueller <florian-ewald.muel...@profitbricks.com>
During testing, I have configured 128 md/raid1's and, while under
heavy IO, I started a check on each of them
(echo check > /sys/block/mdx/md/sync_action).
The CPU utilization went through the ceiling and when looking for
the cause (with 'perf top'). I've discovered that ~50% of the time
was spend in memcmp() called from process_checks().
With this patch applied, it drops to 4% - 10%.
Signed-off-by: Florian-Ewald Mueller <florian-ewald.muel...@profitbricks.com>
[jwang: reformat the commit message]
Signed-off-by: Jack Wang <jinpu.w...@profitbricks.com>
---
lib/string.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/lib/string.c b/lib/string.c
index 2c0900a5d51a..932ef9af2baa 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -852,7 +852,7 @@ EXPORT_SYMBOL(memmove);
* @count: The size of the area.
*/
#undef memcmp
-__visible int memcmp(const void *cs, const void *ct, size_t count)
+static inline int __memcmp(const void *cs, const void *ct, size_t count)
{
const unsigned char *su1, *su2;
int res = 0;
@@ -862,6 +862,20 @@ __visible int memcmp(const void *cs, const void *ct,
size_t count)
break;
return res;
}
+__visible int memcmp(const void *cs, const void *ct, size_t count)
+{
+ const uint64_t *l1p = cs;
+ const uint64_t *l2p = ct;
+
+ while (count >= sizeof(*l1p)) {
+ if (*l1p != *l2p)
+ return __memcmp(l1p, l2p, sizeof(*l1p));
+ count -= sizeof(*l1p);
+ ++l1p;
+ ++l2p;
+ }
+ return __memcmp(l1p, l2p, count);
+}
EXPORT_SYMBOL(memcmp);
#endif
--
2.7.4
