From 6b229cf77d683f634f0edd876c6d1015402303ad Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 8 Dec 2016 11:41:56 -0800 Subject: 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 Signed-off-by: David S. Miller --- net/ipv4/udp.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'net/ipv4') diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index c608334d99aa..5a38faa12cde 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1177,8 +1177,20 @@ out: /* fully reclaim rmem/fwd memory allocated for skb */ static void udp_rmem_release(struct sock *sk, int size, int partial) { + struct udp_sock *up = udp_sk(sk); int amt; + if (likely(partial)) { + up->forward_deficit += size; + size = up->forward_deficit; + if (size < (sk->sk_rcvbuf >> 2) && + !skb_queue_empty(&sk->sk_receive_queue)) + return; + } else { + size += up->forward_deficit; + } + up->forward_deficit = 0; + atomic_sub(size, &sk->sk_rmem_alloc); sk->sk_forward_alloc += size; amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1); -- cgit