[RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain

2014-10-15 Thread Jason Wang 
With the help of xmit_more and virtqueue_enable_cb_avail(), this patch
enable tx interrupt only for the final skb in the chain if
needed. This will help to mitigate tx interrupts.

Cc: Rusty Russell ru...@rustcorp.com.au
Cc: Michael S. Tsirkin m...@redhat.com
Signed-off-by: Jason Wang jasow...@redhat.com
---
 drivers/net/virtio_net.c |   10 +++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2afc2e2..5943f3f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -993,12 +993,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct 
net_device *dev)
virtqueue_disable_cb(sq-vq);
}
}
-   } else if (virtqueue_enable_cb(sq-vq)) {
-   free_old_xmit_skbs(sq, qsize);
}
 
-   if (__netif_subqueue_stopped(dev, qnum) || !skb-xmit_more)
+   if (__netif_subqueue_stopped(dev, qnum) || !skb-xmit_more) {
virtqueue_kick(sq-vq);
+   if (sq-vq-num_free = 2 +MAX_SKB_FRAGS 
+   unlikely(virtqueue_enable_cb_avail(sq-vq))) {
+   free_old_xmit_skbs(sq, qsize);
+   virtqueue_disable_cb(sq-vq);
+   }
+   }
 
return NETDEV_TX_OK;
 }
-- 
1.7.1

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Re: [RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain

2014-10-15 Thread Michael S. Tsirkin 
On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote:
 With the help of xmit_more and virtqueue_enable_cb_avail(), this patch
 enable tx interrupt only for the final skb in the chain if
 needed. This will help to mitigate tx interrupts.
 
 Cc: Rusty Russell ru...@rustcorp.com.au
 Cc: Michael S. Tsirkin m...@redhat.com
 Signed-off-by: Jason Wang jasow...@redhat.com

I think you should split xmit_more stuff out.



 ---
  drivers/net/virtio_net.c |   10 +++---
  1 files changed, 7 insertions(+), 3 deletions(-)
 
 diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
 index 2afc2e2..5943f3f 100644
 --- a/drivers/net/virtio_net.c
 +++ b/drivers/net/virtio_net.c
 @@ -993,12 +993,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, 
 struct net_device *dev)
   virtqueue_disable_cb(sq-vq);
   }
   }
 - } else if (virtqueue_enable_cb(sq-vq)) {
 - free_old_xmit_skbs(sq, qsize);
   }
  
 - if (__netif_subqueue_stopped(dev, qnum) || !skb-xmit_more)
 + if (__netif_subqueue_stopped(dev, qnum) || !skb-xmit_more) {
   virtqueue_kick(sq-vq);
 + if (sq-vq-num_free = 2 +MAX_SKB_FRAGS 
 + unlikely(virtqueue_enable_cb_avail(sq-vq))) {
 + free_old_xmit_skbs(sq, qsize);
 + virtqueue_disable_cb(sq-vq);
 + }
 + }
  
   return NETDEV_TX_OK;
  }
 -- 
 1.7.1
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Re: [RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain

2014-10-15 Thread Jason Wang 
On 10/15/2014 06:22 PM, Michael S. Tsirkin wrote:
 On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote:
 With the help of xmit_more and virtqueue_enable_cb_avail(), this patch
 enable tx interrupt only for the final skb in the chain if
 needed. This will help to mitigate tx interrupts.

 Cc: Rusty Russell ru...@rustcorp.com.au
 Cc: Michael S. Tsirkin m...@redhat.com
 Signed-off-by: Jason Wang jasow...@redhat.com
 I think you should split xmit_more stuff out.

No much difference but if you prefer I will do this.
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Re: [RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain

2014-10-15 Thread Michael S. Tsirkin 
On Wed, Oct 15, 2014 at 06:31:19PM +0800, Jason Wang wrote:
 On 10/15/2014 06:22 PM, Michael S. Tsirkin wrote:
  On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote:
  With the help of xmit_more and virtqueue_enable_cb_avail(), this patch
  enable tx interrupt only for the final skb in the chain if
  needed. This will help to mitigate tx interrupts.
 
  Cc: Rusty Russell ru...@rustcorp.com.au
  Cc: Michael S. Tsirkin m...@redhat.com
  Signed-off-by: Jason Wang jasow...@redhat.com
  I think you should split xmit_more stuff out.
 
 No much difference but if you prefer I will do this.

In fact I did it exactly like this already :)

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