udp: use a separate rx queue for packet reception
under udp flood the sk_receive_queue spinlock is heavily contended.
This patch try to reduce the contention on such lock adding a
second receive queue to the udp sockets; recvmsg() looks first
in such queue and, only if empty, tries to fetch the data from
sk_receive_queue. The latter is spliced into the newly added
queue every time the receive path has to acquire the
sk_receive_queue lock.
The accounting of forward allocated memory is still protected with
the sk_receive_queue lock, so udp_rmem_release() needs to acquire
both locks when the forward deficit is flushed.
On specific scenarios we can end up acquiring and releasing the
sk_receive_queue lock multiple times; that will be covered by
the next patch
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 04862ab..f78fdf8 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -455,7 +455,8 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
return err;
csum_copy_err:
- if (!__sk_queue_drop_skb(sk, skb, flags, udp_skb_destructor)) {
+ if (!__sk_queue_drop_skb(sk, &udp_sk(sk)->reader_queue, skb, flags,
+ udp_skb_destructor)) {
if (is_udp4) {
UDP_INC_STATS(sock_net(sk),
UDP_MIB_CSUMERRORS, is_udplite);
