From 1576d98605998fb59d121a39581129e134217182 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 30 Jun 2016 14:45:36 +0800 Subject: [PATCH] tun: switch to use skb array for tx We used to queue tx packets in sk_receive_queue, this is less efficient since it requires spinlocks to synchronize between producer and consumer. This patch tries to address this by: - switch from sk_receive_queue to a skb_array, and resize it when tx_queue_len was changed. - introduce a new proto_ops peek_len which was used for peeking the skb length. - implement a tun version of peek_len for vhost_net to use and convert vhost_net to use peek_len if possible. Pktgen test shows about 15.3% improvement on guest receiving pps for small buffers: Before: ~1300000pps After : ~1500000pps Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/net/tun.c | 138 +++++++++++++++++++++++++++++++++++++++++--- drivers/vhost/net.c | 16 ++++- include/linux/net.h | 1 + 3 files changed, 146 insertions(+), 9 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 4884802e0af1..74752159ec34 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -71,6 +71,7 @@ #include #include #include +#include #include @@ -167,6 +168,7 @@ struct tun_file { }; struct list_head next; struct tun_struct *detached; + struct skb_array tx_array; }; struct tun_flow_entry { @@ -515,7 +517,11 @@ static struct tun_struct *tun_enable_queue(struct tun_file *tfile) static void tun_queue_purge(struct tun_file *tfile) { - skb_queue_purge(&tfile->sk.sk_receive_queue); + struct sk_buff *skb; + + while ((skb = skb_array_consume(&tfile->tx_array)) != NULL) + kfree_skb(skb); + skb_queue_purge(&tfile->sk.sk_error_queue); } @@ -560,6 +566,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->dev->reg_state == NETREG_REGISTERED) unregister_netdevice(tun->dev); } + if (tun) + skb_array_cleanup(&tfile->tx_array); sock_put(&tfile->sk); } } @@ -613,6 +621,7 @@ static void tun_detach_all(struct net_device *dev) static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filter) { struct tun_file *tfile = file->private_data; + struct net_device *dev = tun->dev; int err; err = security_tun_dev_attach(tfile->socket.sk, tun->security); @@ -642,6 +651,13 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte if (!err) goto out; } + + if (!tfile->detached && + skb_array_init(&tfile->tx_array, dev->tx_queue_len, GFP_KERNEL)) { + err = -ENOMEM; + goto out; + } + tfile->queue_index = tun->numqueues; tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN; rcu_assign_pointer(tfile->tun, tun); @@ -891,8 +907,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) nf_reset(skb); - /* Enqueue packet */ - skb_queue_tail(&tfile->socket.sk->sk_receive_queue, skb); + if (skb_array_produce(&tfile->tx_array, skb)) + goto drop; /* Notify and wake up reader process */ if (tfile->flags & TUN_FASYNC) @@ -1107,7 +1123,7 @@ static unsigned int tun_chr_poll(struct file *file, poll_table *wait) poll_wait(file, sk_sleep(sk), wait); - if (!skb_queue_empty(&sk->sk_receive_queue)) + if (!skb_array_empty(&tfile->tx_array)) mask |= POLLIN | POLLRDNORM; if (sock_writeable(sk) || @@ -1426,22 +1442,61 @@ done: return total; } +static struct sk_buff *tun_ring_recv(struct tun_file *tfile, int noblock, + int *err) +{ + DECLARE_WAITQUEUE(wait, current); + struct sk_buff *skb = NULL; + + skb = skb_array_consume(&tfile->tx_array); + if (skb) + goto out; + if (noblock) { + *err = -EAGAIN; + goto out; + } + + add_wait_queue(&tfile->wq.wait, &wait); + current->state = TASK_INTERRUPTIBLE; + + while (1) { + skb = skb_array_consume(&tfile->tx_array); + if (skb) + break; + if (signal_pending(current)) { + *err = -ERESTARTSYS; + break; + } + if (tfile->socket.sk->sk_shutdown & RCV_SHUTDOWN) { + *err = -EFAULT; + break; + } + + schedule(); + } + + current->state = TASK_RUNNING; + remove_wait_queue(&tfile->wq.wait, &wait); + +out: + return skb; +} + static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, struct iov_iter *to, int noblock) { struct sk_buff *skb; ssize_t ret; - int peeked, err, off = 0; + int err; tun_debug(KERN_INFO, tun, "tun_do_read\n"); if (!iov_iter_count(to)) return 0; - /* Read frames from queue */ - skb = __skb_recv_datagram(tfile->socket.sk, noblock ? MSG_DONTWAIT : 0, - &peeked, &off, &err); + /* Read frames from ring */ + skb = tun_ring_recv(tfile, noblock, &err); if (!skb) return err; @@ -1574,8 +1629,25 @@ out: return ret; } +static int tun_peek_len(struct socket *sock) +{ + struct tun_file *tfile = container_of(sock, struct tun_file, socket); + struct tun_struct *tun; + int ret = 0; + + tun = __tun_get(tfile); + if (!tun) + return 0; + + ret = skb_array_peek_len(&tfile->tx_array); + tun_put(tun); + + return ret; +} + /* Ops structure to mimic raw sockets with tun */ static const struct proto_ops tun_socket_ops = { + .peek_len = tun_peek_len, .sendmsg = tun_sendmsg, .recvmsg = tun_recvmsg, }; @@ -2397,6 +2469,53 @@ static const struct ethtool_ops tun_ethtool_ops = { .get_ts_info = ethtool_op_get_ts_info, }; +static int tun_queue_resize(struct tun_struct *tun) +{ + struct net_device *dev = tun->dev; + struct tun_file *tfile; + struct skb_array **arrays; + int n = tun->numqueues + tun->numdisabled; + int ret, i; + + arrays = kmalloc(sizeof *arrays * n, GFP_KERNEL); + if (!arrays) + return -ENOMEM; + + for (i = 0; i < tun->numqueues; i++) { + tfile = rtnl_dereference(tun->tfiles[i]); + arrays[i] = &tfile->tx_array; + } + list_for_each_entry(tfile, &tun->disabled, next) + arrays[i++] = &tfile->tx_array; + + ret = skb_array_resize_multiple(arrays, n, + dev->tx_queue_len, GFP_KERNEL); + + kfree(arrays); + return ret; +} + +static int tun_device_event(struct notifier_block *unused, + unsigned long event, void *ptr) +{ + struct net_device *dev = netdev_notifier_info_to_dev(ptr); + struct tun_struct *tun = netdev_priv(dev); + + switch (event) { + case NETDEV_CHANGE_TX_QUEUE_LEN: + if (tun_queue_resize(tun)) + return NOTIFY_BAD; + break; + default: + break; + } + + return NOTIFY_DONE; +} + +static struct notifier_block tun_notifier_block __read_mostly = { + .notifier_call = tun_device_event, +}; static int __init tun_init(void) { @@ -2416,6 +2535,8 @@ static int __init tun_init(void) pr_err("Can't register misc device %d\n", TUN_MINOR); goto err_misc; } + + register_netdevice_notifier(&tun_notifier_block); return 0; err_misc: rtnl_link_unregister(&tun_link_ops); @@ -2427,6 +2548,7 @@ static void tun_cleanup(void) { misc_deregister(&tun_miscdev); rtnl_link_unregister(&tun_link_ops); + unregister_netdevice_notifier(&tun_notifier_block); } /* Get an underlying socket object from tun file. Returns error unless file is diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 1d3e45f84549..e032ca397371 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -481,10 +481,14 @@ out: static int peek_head_len(struct sock *sk) { + struct socket *sock = sk->sk_socket; struct sk_buff *head; int len = 0; unsigned long flags; + if (sock->ops->peek_len) + return sock->ops->peek_len(sock); + spin_lock_irqsave(&sk->sk_receive_queue.lock, flags); head = skb_peek(&sk->sk_receive_queue); if (likely(head)) { @@ -497,6 +501,16 @@ static int peek_head_len(struct sock *sk) return len; } +static int sk_has_rx_data(struct sock *sk) +{ + struct socket *sock = sk->sk_socket; + + if (sock->ops->peek_len) + return sock->ops->peek_len(sock); + + return skb_queue_empty(&sk->sk_receive_queue); +} + static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk) { struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX]; @@ -513,7 +527,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk) endtime = busy_clock() + vq->busyloop_timeout; while (vhost_can_busy_poll(&net->dev, endtime) && - skb_queue_empty(&sk->sk_receive_queue) && + !sk_has_rx_data(sk) && vhost_vq_avail_empty(&net->dev, vq)) cpu_relax_lowlatency(); diff --git a/include/linux/net.h b/include/linux/net.h index 25aa03b51c4e..b9f0ff4d489c 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -185,6 +185,7 @@ struct proto_ops { ssize_t (*splice_read)(struct socket *sock, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags); int (*set_peek_off)(struct sock *sk, int val); + int (*peek_len)(struct socket *sock); }; #define DECLARE_SOCKADDR(type, dst, src) \