Re: [RFC] packet: change call of synchronize_net to call_rcu
From: Daniel Borkmann <hidden>
Date: 2012-09-04 15:17:01
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lkml
On Tue, Sep 4, 2012 at 4:16 PM, Iulius Curt [off-list ref] wrote:
synchronize_net is called every time we close a PF_PACKET socket which is causing performance loss when doing this on many sockets.
Do you have any particular use case in mind? I can imagine if you are closing a PF_PACKET socket in a network analyzer application, you're more or less out of its 'critical path' anyway.
quoted hunk ↗ jump to hunk
Signed-off-by: Sorin Dumitru <redacted> Signed-off-by: Iulius Curt <redacted> --- Statistics using test program [1] Sockets count | Not patched | Patched _________________________________________ 1 000 000 | 1.28 s | 1.22 s 5 000 000 | 7.3 s | 6.25 s 50 000 000 | 72.89 s | 64.41 s [1] http://pastebin.com/xQ9BziaP --- net/packet/af_packet.c | 46 ++++++++++++++++++++++++++++++++++++---------- net/packet/internal.h | 1 + 2 files changed, 37 insertions(+), 10 deletions(-)diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 5dafe84..7b60135 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c@@ -2299,6 +2299,32 @@ static int packet_sendmsg(struct kiocb *iocb, struct socket *sock, return packet_snd(sock, msg, len); } +void packet_release_finish(struct sock *sk, int null) +{ + struct socket *sock = sk->sk_socket; + + sock_orphan(sk); + /* Modifing this after the socket has been released + * might lead to memory corruption so we don't do it */ + if (null) + sock->sk = NULL;
One minor remark: please don't name this variable "null" since it can have a value of 0 or 1 in your code, it's a bit misleading. Maybe rather "nullify" or something.
quoted hunk ↗ jump to hunk
+ /* Purge queues */ + + skb_queue_purge(&sk->sk_receive_queue); + sk_refcnt_debug_release(sk); + + sock_put(sk); +} + +void packet_release_rcu(struct rcu_head *rcu) +{ + struct packet_sock *po = container_of(rcu, struct packet_sock, rcu_head); + struct sock *sk = &po->sk; + + packet_release_finish(sk, 0); +} + /* * Close a PACKET socket. This is fairly simple. We immediately go * to 'closed' state and remove our protocol entry in the device list.@@ -2310,6 +2336,7 @@ static int packet_release(struct socket *sock) struct packet_sock *po; struct net *net; union tpacket_req_u req_u; + int postpone = 0; if (!sk) return 0;@@ -2326,7 +2353,10 @@ static int packet_release(struct socket *sock) preempt_enable(); spin_lock(&po->bind_lock); - unregister_prot_hook(sk, false); + if (po->running) { + postpone = 1; + __unregister_prot_hook(sk, false); + } if (po->prot_hook.dev) { dev_put(po->prot_hook.dev); po->prot_hook.dev = NULL;@@ -2345,19 +2375,15 @@ static int packet_release(struct socket *sock) fanout_release(sk); - synchronize_net(); /* * Now the socket is dead. No more input will appear. */ - sock_orphan(sk); - sock->sk = NULL; - - /* Purge queues */ - - skb_queue_purge(&sk->sk_receive_queue); - sk_refcnt_debug_release(sk); + if (postpone) { + call_rcu(&po->rcu_head, packet_release_rcu); + return 0; + } - sock_put(sk); + packet_release_finish(sk, 1); return 0; }diff --git a/net/packet/internal.h b/net/packet/internal.h index 44945f6..5778c12 100644 --- a/net/packet/internal.h +++ b/net/packet/internal.h@@ -104,6 +104,7 @@ struct packet_sock { int ifindex; /* bound device */ __be16 num; struct packet_mclist *mclist; + struct rcu_head rcu_head; atomic_t mapped; enum tpacket_versions tp_version; unsigned int tp_hdrlen; --1.7.9.5