linux-kernel - [PATCH 3/3] mm: kmem: switch to static_branch_likely() in memcg_kmem

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 7 Jul 2020 10:36:12 -0700
From:   Roman Gushchin <guro@...com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>, <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>, <kernel-team@...com>,
        <linux-kernel@...r.kernel.org>, Roman Gushchin <guro@...com>
Subject: [PATCH 3/3] mm: kmem: switch to static_branch_likely() in memcg_kmem_enabled()

Currently memcg_kmem_enabled() is optimized for the kernel memory
accounting being off. It was so for a long time, and arguably the
reason behind was that the kernel memory accounting was initially an
opt-in feature. However, now it's on by default on both cgroup v1
and cgroup v2, and it's on for all cgroups. So let's switch over
to static_branch_likely() to reflect this fact.

Unlikely there is a significant performance difference, as the cost
of a memory allocation and its accounting significantly exceeds the
cost of a jump. However, the conversion makes the code look more
logically.

Signed-off-by: Roman Gushchin <guro@...com>
---
 include/linux/memcontrol.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b8f52a3fed90..ab9322215b2e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1456,7 +1456,7 @@ void memcg_put_cache_ids(void);

 static inline bool memcg_kmem_enabled(void)
 {
-	return static_branch_unlikely(&memcg_kmem_enabled_key);
+	return static_branch_likely(&memcg_kmem_enabled_key);
 }

 static inline bool memcg_kmem_bypass(void)
-- 
2.26.2