From 1240d1373cd7f874dd0f3057c3e9643e71ef75c6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 8 Nov 2009 10:18:44 +0000 Subject: [PATCH] ipv4: udp: Optimise multicast reception UDP multicast rx path is a bit complex and can hold a spinlock for a long time. Using a small (32 or 64 entries) stack of socket pointers can help to perform expensive operations (skb_clone(), udp_queue_rcv_skb()) outside of the lock, in most cases. It's also a base for a future RCU conversion of multicast recption. Signed-off-by: Eric Dumazet Signed-off-by: Lucian Adrian Grijincu Signed-off-by: David S. Miller --- net/ipv4/udp.c | 76 +++++++++++++++++++++++++++++++++----------------- 1 file changed, 50 insertions(+), 26 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index dd7f3d20989a..9d9072c6cce7 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1329,49 +1329,73 @@ drop: return -1; } + +static void flush_stack(struct sock **stack, unsigned int count, + struct sk_buff *skb, unsigned int final) +{ + unsigned int i; + struct sk_buff *skb1 = NULL; + + for (i = 0; i < count; i++) { + if (likely(skb1 == NULL)) + skb1 = (i == final) ? skb : skb_clone(skb, GFP_ATOMIC); + + if (skb1 && udp_queue_rcv_skb(stack[i], skb1) <= 0) + skb1 = NULL; + } + if (unlikely(skb1)) + kfree_skb(skb1); +} + /* * Multicasts and broadcasts go to each listener. * - * Note: called only from the BH handler context, - * so we don't need to lock the hashes. + * Note: called only from the BH handler context. */ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb, struct udphdr *uh, __be32 saddr, __be32 daddr, struct udp_table *udptable) { - struct sock *sk; + struct sock *sk, *stack[256 / sizeof(struct sock *)]; struct udp_hslot *hslot = udp_hashslot(udptable, net, ntohs(uh->dest)); int dif; + unsigned int i, count = 0; spin_lock(&hslot->lock); sk = sk_nulls_head(&hslot->head); dif = skb->dev->ifindex; sk = udp_v4_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif); - if (sk) { - struct sock *sknext = NULL; - - do { - struct sk_buff *skb1 = skb; - - sknext = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest, - daddr, uh->source, saddr, - dif); - if (sknext) - skb1 = skb_clone(skb, GFP_ATOMIC); - - if (skb1) { - int ret = udp_queue_rcv_skb(sk, skb1); - if (ret > 0) - /* we should probably re-process instead - * of dropping packets here. */ - kfree_skb(skb1); - } - sk = sknext; - } while (sknext); - } else - consume_skb(skb); + while (sk) { + stack[count++] = sk; + sk = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest, + daddr, uh->source, saddr, dif); + if (unlikely(count == ARRAY_SIZE(stack))) { + if (!sk) + break; + flush_stack(stack, count, skb, ~0); + count = 0; + } + } + /* + * before releasing chain lock, we must take a reference on sockets + */ + for (i = 0; i < count; i++) + sock_hold(stack[i]); + spin_unlock(&hslot->lock); + + /* + * do the slow work with no lock held + */ + if (count) { + flush_stack(stack, count, skb, count - 1); + + for (i = 0; i < count; i++) + sock_put(stack[i]); + } else { + kfree_skb(skb); + } return 0; } -- 2.20.1