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authorAbel Wu <wuyun.wu@huawei.com>2020-10-14 02:48:40 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-14 04:38:27 +0300
commitc270cf3041a5cb7c5853d45a794309e66576493a (patch)
tree53ec5da29e62574e8b50ce6bd1019c7e02964ad6 /mm/slub.c
parentd7cff4ded857ff7cc3e49eb39cc14df9345b9662 (diff)
downloadlinux-c270cf3041a5cb7c5853d45a794309e66576493a.tar.xz
mm/slub.c: branch optimization in free slowpath
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@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Hewenliang <hewenliang4@huawei.com> Cc: Hu Shiyuan <hushiyuan@huawei.com> Link: http://lkml.kernel.org/r/20200813101812.1617-1-wuyun.wu@huawei.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c23
1 files changed, 12 insertions, 11 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 6d3574013b2f..da6438bd8202 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3019,20 +3019,21 @@ 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;
}