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authorEric Dumazet <edumazet@google.com>2016-12-08 11:41:56 -0800
committerDavid S. Miller <davem@davemloft.net>2016-12-09 22:12:21 -0500
commit6b229cf77d683f634f0edd876c6d1015402303ad (patch)
treeec877d3e324da74f7bbb179d4cd4a8db0172865c /net
parentc84d949057cab262b4d3110ead9a42a58c2958f7 (diff)
downloadlinux-6b229cf77d683f634f0edd876c6d1015402303ad.tar.bz2
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/udp.c12
1 files changed, 12 insertions, 0 deletions
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);