netdev - [PATCH net-next] udp/v6: prefetch rmem_alloc in udp6_queue_rcv

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Message-Id: <9152ab05a2fe6b6230b44b7a23056b367ca19f5e.1498127002.git.pabeni@redhat.com>
Date:   Thu, 22 Jun 2017 15:01:22 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>
Subject: [PATCH net-next] udp/v6: prefetch rmem_alloc in udp6_queue_rcv_skb()

very similar to commit dd99e425be23 ("udp: prefetch
rmem_alloc in udp_queue_rcv_skb()"), this allows saving a cache
miss when the BH is bottle-neck for UDP over ipv6 packet
processing, e.g. for small packets when a single RX NIC ingress
queue is in use.

Performances under flood when multiple NIC RX queues used are
unaffected, but when a single NIC rx queue is in use, this
gives ~8% performance improvement.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv6/udp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2b33847..d1d7288 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -630,6 +630,7 @@ static int udpv6_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;
-- 
2.9.4