From: Abel Wu <wuyun.wu@xxxxxxxxxx>
The two conditions are mutually exclusive and gcc compiler will
optimise this into if-else-like pattern. Given that the majority
of free_slowpath is free_frozen, let's provide some hint to the
compilers.
Tests (perf bench sched messaging -g 20 -l 400000, executed 10x
after reboot) are done and the summarized result:
un-patched patched
max. 192.316 189.851
min. 187.267 186.252
avg. 189.154 188.086
stdev. 1.37 0.99
Signed-off-by: Abel Wu <wuyun.wu@xxxxxxxxxx>
---
mm/slub.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 4f496ae5a820..f9182a760675 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2958,20 +2958,21 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
if (likely(!n)) {
- /*
- * If we just froze the page then put it onto the
- * per cpu partial list.
- */
- if (new.frozen && !was_frozen) {
+ if (likely(was_frozen)) {
+ /*
+ * The list lock was not taken therefore no list
+ * activity can be necessary.
+ */
+ stat(s, FREE_FROZEN);
+ } else if (new.frozen) {
+ /*
+ * If we just froze the page then put it onto the
+ * per cpu partial list.
+ */
put_cpu_partial(s, page, 1);
stat(s, CPU_PARTIAL_FREE);
}
- /*
- * The list lock was not taken therefore no list
- * activity can be necessary.
- */
- if (was_frozen)
- stat(s, FREE_FROZEN);
+
return;
}
--
2.28.0.windows.1
