Re: [Xen-devel] [PATCH net-next v3 8/9] xen-netback: Timeout packets in RX path

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 09/01/14 09:20, Paul Durrant wrote:
> > We are adding the skb to vif->rx_queue even when
> > xenvif_rx_ring_slots_available(vif, min_slots_needed) said there is no
> > space for that. Or am I missing something? Paul?
> That's correct. Part of the flow control improvement was to get rid of needless 
> packet drops. For your purposes, you basically need to avoid using the queuing 
> discipline and take packets into netback's vif->rx_queue regardless of the state 
> of the shared ring so that you can drop them if they get beyond a certain age. So, 
> perhaps you should never stop the netif queue, place an upper limit on 
> vif->rx_queue (either packet or byte count) and drop when that is exceeded (i.e. 
> mimicking pfifo or bfifo internally).
How about this:
- when the timer fires first we wake up the thread an tell it to drop 
all the packets in rx_queue
- start_xmit then can drain the qdisc queue into the device queue
- additionally, the RX thread should stop that timer when it was able to 
do some work
Regards,

Zoli

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