Re: [PATCH net-next V3 6/6] tun: switch to use skb array for tx

[kbuild test robot]

Hi,

[auto build test WARNING on net-next/master]

url:
https://github.com/0day-ci/linux/commits/Jason-Wang/switch-to-use-tx-skb-array-in-tun/20160630-120656


coccinelle warnings: (new ones prefixed by >>)

>> drivers/net/tun.c:1476:2-3: Unneeded semicolon

Please review and possibly fold the followup patch.

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation

[PATCH net-next V3 6/6] tun: switch to use skb array for tx

[Jason Wang]

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: ~130pps
After : ~150pps

Signed-off-by: Jason Wang 
---
 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 4884802..3be69ea 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(>sk.sk_receive_queue);
+   struct sk_buff *skb;
+
+   while ((skb = skb_array_consume(>tx_array)) != NULL)
+   kfree_skb(skb);
+
skb_queue_purge(>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(>tx_array);
sock_put(>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(>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(>socket.sk->sk_receive_queue, skb);
+   if (skb_array_produce(>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_receive_queue))
+   if (!skb_array_empty(>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(>tx_array);
+   if (skb)
+   goto out;
+   if (noblock) {
+   *err = -EAGAIN;
+   goto out;
+   }
+
+   add_wait_queue(>wq.wait, );
+   current->state = TASK_INTERRUPTIBLE;
+
+   while (1) {
+   skb = skb_array_consume(>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(>wq.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