From: Soheil Hassas Yeganeh <soheil@google.com>
Date: Thu, 4 Jan 2018 02:47:10 +0000 (-0500)
Subject: ip: do not set RFS core on error queue reads
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=e3f2c4a3db1413bebfd502f7ac94fb55e3ba8c84;p=openwrt%2Fstaging%2Fblogic.git

ip: do not set RFS core on error queue reads

We should only record RPS on normal reads and writes.
In single threaded processes, all calls record the same state. In
multi-threaded processes where a separate thread processes
errors, the RFS table mispredicts.

Note that, when CONFIG_RPS is disabled, sock_rps_record_flow
is a noop and no branch is added as a result of this patch.

Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index bab98a4fedad..54cccdd8b1e3 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -790,7 +790,8 @@ int inet_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 	int addr_len = 0;
 	int err;
 
-	sock_rps_record_flow(sk);
+	if (likely(!(flags & MSG_ERRQUEUE)))
+		sock_rps_record_flow(sk);
 
 	err = sk->sk_prot->recvmsg(sk, msg, size, flags & MSG_DONTWAIT,
 				   flags & ~MSG_DONTWAIT, &addr_len);