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udp: use a separate rx queue for packet reception

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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>
This commit is contained in:
Paolo Abeni
2017-05-16 11:20:14 +02:00
committed by David S. Miller
parent 65101aeca5
commit 2276f58ac5
5 changed files with 131 additions and 24 deletions
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9
include/net/udp.h
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@@ -249,13 +249,8 @@ void udp_destruct_sock(struct sock *sk);
void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
void udp_skb_destructor(struct sock *sk, struct sk_buff *skb);
static inline struct sk_buff *
__skb_recv_udp(struct sock *sk, unsigned int flags, int noblock, int *peeked,
int *off, int *err)
{
return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
udp_skb_destructor, peeked, off, err);
}
struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
int noblock, int *peeked, int *off, int *err);
static inline struct sk_buff *skb_recv_udp(struct sock *sk, unsigned int flags,
int noblock, int *err)
{