From: Paolo Abeni <pabeni@redhat.com>
Date: Wed, 21 Jun 2017 08:24:40 +0000 (+0200)
Subject: udp: prefetch rmem_alloc in udp_queue_rcv_skb()
X-Git-Tag: v4.13-rc1~157^2~125
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=dd99e425be23;p=karo-tx-linux.git

udp: prefetch rmem_alloc in udp_queue_rcv_skb()

On UDP packets processing, if the BH is the bottle-neck, it
always sees a cache miss while updating rmem_alloc; try to
avoid it prefetching the value as soon as we have the socket
available.

Performances under flood with multiple NIC rx queues used are
unaffected, but when a single NIC rx queue is in use, this
gives ~10% performance improvement.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index f3450f092d71..067a607917f9 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1949,6 +1949,7 @@ static int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		}
 	}
 
+	prefetch(&sk->sk_rmem_alloc);
 	if (rcu_access_pointer(sk->sk_filter) &&
 	    udp_lib_checksum_complete(skb))
 			goto csum_error;