[PATCH v2 1/5] cgroup: Only update sk_cgrp_prioidx on change

[Daniel Wagner <wagi@monom.org>]

From: Daniel Wagner <daniel.wagner@bmw-carit.de>

Do not make the cache line dirty when nothing has changed.
sock_update_classid() does exactly the same thing.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
---
 net/core/sock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 929bdcc..bbab10d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1182,10 +1182,14 @@ EXPORT_SYMBOL(sock_update_classid);
 
 void sock_update_netprioidx(struct sock *sk)
 {
+	u32 prioidx;
+
 	if (in_interrupt())
 		return;
 
-	sk->sk_cgrp_prioidx = task_netprioidx(current);
+	prioidx = task_netprioidx(current);
+	if (prioidx != sk->sk_cgrp_prioidx)
+		sk->sk_cgrp_prioidx = prioidx;
 }
 EXPORT_SYMBOL_GPL(sock_update_netprioidx);
 #endif
-- 
1.7.11.1.165.g299666c