From: Paolo Abeni Date: Wed, 21 Jun 2017 09:45:31 +0000 (+0200) Subject: sock: avoid dirtying incoming_cpu if not needed X-Git-Tag: v4.13-rc1~157^2~123 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=34cfb542b5b1762c73479a4a61e0a3b77253f876;p=linux.git sock: avoid dirtying incoming_cpu if not needed for connected socket, the incoming_cpu field in the sock struct is not going to change frequently, but we are setting it unconditionally for each packet. Since sk_incoming_cpu and sk_flags share the same cacheline, and the latter is access by udp_recvmsg(), this cause a cache miss for each packet for UDP connected socket. With this patch, we set the incoming cpu field only when the ingress cpu really changes. This gives a small but measurable performance improvement for connected UDP socket. Signed-off-by: Paolo Abeni Signed-off-by: David S. Miller --- diff --git a/include/net/sock.h b/include/net/sock.h index 858891c36f94..00d09140e354 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -907,7 +907,10 @@ static inline int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb) static inline void sk_incoming_cpu_update(struct sock *sk) { - sk->sk_incoming_cpu = raw_smp_processor_id(); + int cpu = raw_smp_processor_id(); + + if (unlikely(sk->sk_incoming_cpu != cpu)) + sk->sk_incoming_cpu = cpu; } static inline void sock_rps_record_flow_hash(__u32 hash)