macvtap: switch to use skb array

This patch switch to use skb array instead of sk_receive_queue to
avoid spinlock contentions. Tests shows about 21% improvements for
guest rx pps:

Before: 1472731 pkts/s
After:  1786289 pkts/s

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 71 insertions, 11 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 2476923b424d..9204d19fb30c 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -21,6 +21,7 @@
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <linux/virtio_net.h>
+#include <linux/skb_array.h>
 
 /*
  * A macvtap queue is the central object of this driver, it connects
@@ -43,6 +44,7 @@ struct macvtap_queue {
         u16 queue_index;
         bool enabled;
         struct list_head next;
+        struct skb_array skb_array;
 };
 
 #define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
@@ -273,6 +275,7 @@ static void macvtap_put_queue(struct macvtap_queue *q)
         rtnl_unlock();
 
         synchronize_rcu();
+        skb_array_cleanup(&q->skb_array);
         sock_put(&q->sk);
 }
 
@@ -366,7 +369,7 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
         if (!q)
                 return RX_HANDLER_PASS;
 
-        if (skb_queue_len(&q->sk.sk_receive_queue) >= dev->tx_queue_len)
+        if (__skb_array_full(&q->skb_array))
                 goto drop;
 
         skb_push(skb, ETH_HLEN);
@@ -384,7 +387,8 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
                         goto drop;
 
                 if (!segs) {
-                        skb_queue_tail(&q->sk.sk_receive_queue, skb);
+                        if (skb_array_produce(&q->skb_array, skb))
+                                goto drop;
                         goto wake_up;
                 }
 
@@ -393,7 +397,11 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
                         struct sk_buff *nskb = segs->next;
 
                         segs->next = NULL;
-                        skb_queue_tail(&q->sk.sk_receive_queue, segs);
+                        if (skb_array_produce(&q->skb_array, segs)) {
+                                kfree_skb(segs);
+                                kfree_skb_list(nskb);
+                                break;
+                        }
                         segs = nskb;
                 }
         } else {
@@ -406,7 +414,8 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
                     !(features & NETIF_F_CSUM_MASK) &&
                     skb_checksum_help(skb))
                         goto drop;
-                skb_queue_tail(&q->sk.sk_receive_queue, skb);
+                if (skb_array_produce(&q->skb_array, skb))
+                        goto drop;
         }
 
 wake_up:
@@ -523,7 +532,11 @@ static void macvtap_sock_write_space(struct sock *sk)
 
 static void macvtap_sock_destruct(struct sock *sk)
 {
-        skb_queue_purge(&sk->sk_receive_queue);
+        struct macvtap_queue *q = container_of(sk, struct macvtap_queue, sk);
+        struct sk_buff *skb;
+
+        while ((skb = skb_array_consume(&q->skb_array)) != NULL)
+                kfree(skb);
 }
 
 static int macvtap_open(struct inode *inode, struct file *file)
@@ -536,13 +549,13 @@ static int macvtap_open(struct inode *inode, struct file *file)
         rtnl_lock();
         dev = dev_get_by_macvtap_minor(iminor(inode));
         if (!dev)
-                goto out;
+                goto err;
 
         err = -ENOMEM;
         q = (struct macvtap_queue *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
                                              &macvtap_proto, 0);
         if (!q)
-                goto out;
+                goto err;
 
         RCU_INIT_POINTER(q->sock.wq, &q->wq);
         init_waitqueue_head(&q->wq.wait);
@@ -566,11 +579,24 @@ static int macvtap_open(struct inode *inode, struct file *file)
         if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
                 sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 
+        err = -ENOMEM;
+        if (skb_array_init(&q->skb_array, dev->tx_queue_len, GFP_KERNEL))
+                goto err_array;
+
         err = macvtap_set_queue(dev, file, q);
         if (err)
-                sock_put(&q->sk);
+                goto err_queue;
 
-out:
+        dev_put(dev);
+
+        rtnl_unlock();
+        return err;
+
+err_queue:
+        skb_array_cleanup(&q->skb_array);
+err_array:
+        sock_put(&q->sk);
+err:
         if (dev)
                 dev_put(dev);
 
@@ -596,7 +622,7 @@ static unsigned int macvtap_poll(struct file *file, poll_table * wait)
         mask = 0;
         poll_wait(file, &q->wq.wait, wait);
 
-        if (!skb_queue_empty(&q->sk.sk_receive_queue))
+        if (!skb_array_empty(&q->skb_array))
                 mask |= POLLIN | POLLRDNORM;
 
         if (sock_writeable(&q->sk) ||
@@ -856,7 +882,7 @@ static ssize_t macvtap_do_read(struct macvtap_queue *q,
                                         TASK_INTERRUPTIBLE);
 
                 /* Read frames from the queue */
-                skb = skb_dequeue(&q->sk.sk_receive_queue);
+                skb = skb_array_consume(&q->skb_array);
                 if (skb)
                         break;
                 if (noblock) {
@@ -1180,10 +1206,18 @@ static int macvtap_recvmsg(struct socket *sock, struct msghdr *m,
         return ret;
 }
 
+static int macvtap_peek_len(struct socket *sock)
+{
+        struct macvtap_queue *q = container_of(sock, struct macvtap_queue,
+                                               sock);
+        return skb_array_peek_len(&q->skb_array);
+}
+
 /* Ops structure to mimic raw sockets with tun */
 static const struct proto_ops macvtap_socket_ops = {
         .sendmsg = macvtap_sendmsg,
         .recvmsg = macvtap_recvmsg,
+        .peek_len = macvtap_peek_len,
 };
 
 /* Get an underlying socket object from tun file.  Returns error unless file is
@@ -1202,6 +1236,28 @@ struct socket *macvtap_get_socket(struct file *file)
 }
 EXPORT_SYMBOL_GPL(macvtap_get_socket);
 
+static int macvtap_queue_resize(struct macvlan_dev *vlan)
+{
+        struct net_device *dev = vlan->dev;
+        struct macvtap_queue *q;
+        struct skb_array **arrays;
+        int n = vlan->numqueues;
+        int ret, i = 0;
+
+        arrays = kmalloc(sizeof *arrays * n, GFP_KERNEL);
+        if (!arrays)
+                return -ENOMEM;
+
+        list_for_each_entry(q, &vlan->queue_list, next)
+                arrays[i++] = &q->skb_array;
+
+        ret = skb_array_resize_multiple(arrays, n,
+                                        dev->tx_queue_len, GFP_KERNEL);
+
+        kfree(arrays);
+        return ret;
+}
+
 static int macvtap_device_event(struct notifier_block *unused,
                                 unsigned long event, void *ptr)
 {
@@ -1249,6 +1305,10 @@ static int macvtap_device_event(struct notifier_block *unused,
                 device_destroy(&macvtap_class, devt);
                 macvtap_free_minor(vlan);
                 break;
+        case NETDEV_CHANGE_TX_QUEUE_LEN:
+                if (macvtap_queue_resize(vlan))
+                        return NOTIFY_BAD;
+                break;
         }
 
         return NOTIFY_DONE;