Re: [Xen-devel] [PATCH] Remove the 500ms timeout to restart the netif queue.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Dec 14, 2010 at 08:35:20PM +0000, Paul Durrant wrote:
> It is generally unhelpful as it results in a massive tail-drop should a guest 
> become
> unresponsive for a relatively short period of time and no back-pressure 
> (other than
> that caused by a higher layer protocol) is applied to the sender.

The patch just removes the timeout, so the queue will be considered 
unavailable..
So will the queue be restarted via the net_rx_action logic?

> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
>  drivers/xen/netback/netback.c |   20 +-------------------
>  1 files changed, 1 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/xen/netback/netback.c b/drivers/xen/netback/netback.c
> index 066d140..87a2cd4 100644
> --- a/drivers/xen/netback/netback.c
> +++ b/drivers/xen/netback/netback.c
> @@ -271,13 +271,6 @@ static inline int netbk_queue_full(struct xen_netif 
> *netif)
>              ((netif->rx.rsp_prod_pvt + NET_RX_RING_SIZE - peek) < needed);
>  }
>  
> -static void tx_queue_callback(unsigned long data)
> -{
> -     struct xen_netif *netif = (struct xen_netif *)data;
> -     if (netif_schedulable(netif))
> -             netif_wake_queue(netif->dev);
> -}
> -
>  /* Figure out how many ring slots we're going to need to send @skb to
>     the guest. */
>  static unsigned count_skb_slots(struct sk_buff *skb, struct xen_netif *netif)
> @@ -360,19 +353,8 @@ int netif_be_start_xmit(struct sk_buff *skb, struct 
> net_device *dev)
>               netif->rx.sring->req_event = netif->rx_req_cons_peek +
>                       netbk_max_required_rx_slots(netif);
>               mb(); /* request notification /then/ check & stop the queue */
> -             if (netbk_queue_full(netif)) {
> +             if (netbk_queue_full(netif))
>                       netif_stop_queue(dev);
> -                     /*
> -                      * Schedule 500ms timeout to restart the queue, thus
> -                      * ensuring that an inactive queue will be drained.
> -                      * Packets will be immediately be dropped until more
> -                      * receive buffers become available (see
> -                      * netbk_queue_full() check above).
> -                      */
> -                     netif->tx_queue_timeout.data = (unsigned long)netif;
> -                     netif->tx_queue_timeout.function = tx_queue_callback;
> -                     mod_timer(&netif->tx_queue_timeout, jiffies + HZ/2);
> -             }
>       }
>       skb_queue_tail(&netbk->rx_queue, skb);
>  
> -- 
> 1.5.6.5
> 
> 
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