udp: add batching to udp_rmem_release()
If udp_recvmsg() constantly releases sk_rmem_alloc
for every read packet, it gives opportunity for
producers to immediately grab spinlocks and desperatly
try adding another packet, causing false sharing.
We can add a simple heuristic to give the signal
by batches of ~25 % of the queue capacity.
This patch considerably increases performance under
flood by about 50 %, since the thread draining the queue
is no longer slowed by false sharing.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/udp.h b/include/linux/udp.h
index d1fd8cd..c0f5308 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -79,6 +79,9 @@ struct udp_sock {
int (*gro_complete)(struct sock *sk,
struct sk_buff *skb,
int nhoff);
+
+ /* This field is dirtied by udp_recvmsg() */
+ int forward_deficit;
};
static inline struct udp_sock *udp_sk(const struct sock *sk)