net: ipv4 only populate IP_PKTINFO when needed
The since the removal of the routing cache computing
fib_compute_spec_dst() does a fib_table lookup for each UDP multicast
packet received. This has introduced a performance regression for some
UDP workloads.
This change skips populating the packet info for sockets that do not have
IP_PKTINFO set.
Benchmark results from a netperf UDP_RR test:
Before 89789.68 transactions/s
After 90587.62 transactions/s
Benchmark results from a fio 1 byte UDP multicast pingpong test
(Multicast one way unicast response):
Before 12.63us RTT
After 12.48us RTT
Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 262ea39..4226c53 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1544,7 +1544,7 @@
rc = 0;
- ipv4_pktinfo_prepare(skb);
+ ipv4_pktinfo_prepare(sk, skb);
bh_lock_sock(sk);
if (!sock_owned_by_user(sk))
rc = __udp_queue_rcv_skb(sk, skb);