From 34cfb542b5b1762c73479a4a61e0a3b77253f876 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Wed, 21 Jun 2017 11:45:31 +0200 Subject: [PATCH] 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 --- include/net/sock.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) 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) -- 2.20.1