netdev - [PATCH net-next] udp: use sk_protocol instead of pcflag to detect udplite sockets

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Message-Id: <fc91ec83ecf454fad74c326380203a34434cb1ec.1490953526.git.pabeni@redhat.com>
Date:   Fri, 31 Mar 2017 11:47:39 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] udp: use sk_protocol instead of pcflag to detect udplite sockets

In the udp_sock struct, the 'forward_deficit' and 'pcflag' fields
share the same cacheline. While the first is dirtied by
udp_recvmsg, the latter is read, possibly several times, by the
bottom half processing to discriminate between udp and udplite
sockets.

With this patch, sk->sk_protocol is used to check is the socket is
really an udplite one, avoiding some cache misses per
packet and improving the performance under udp_flood with
small packet up to 10%.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 include/linux/udp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/udp.h b/include/linux/udp.h
index c0f5308..6cb4061 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -115,6 +115,6 @@ static inline bool udp_get_no_check6_rx(struct sock *sk)
 #define udp_portaddr_for_each_entry_rcu(__sk, list) \
 	hlist_for_each_entry_rcu(__sk, list, __sk_common.skc_portaddr_node)

-#define IS_UDPLITE(__sk) (udp_sk(__sk)->pcflag)
+#define IS_UDPLITE(__sk) (__sk->sk_protocol == IPPROTO_UDPLITE)

 #endif	/* _LINUX_UDP_H */
-- 
2.9.3