Re: [Xen-devel] vif tx drops

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> 
> " Are the drops happening at a slow, steady rate? Or are they perhaps
> " all happening during domain startup and then there are no more drops?
> 
> The drop rate is high right after a xenU startup (16% when I just tried it),
> then the rate slows to just under 1% of packets in steady state.
> 

Please try changing the following line in netfront.c:
#define RX_MIN_TARGET 8
to:
#define RX_MIN_TARGET NETIF_RX_RING_SIZE

This will turn off the attempts to dynamically adjust the number of
receive buffers queued up to receive packets. This strategy can lose
packets if traffic is bursty -- also, if the domain is occasionally
preempted, packets can queue up and overflow a buffer allowance that
is otherwise sufficient.

If you find that this sorts out your packet-loss problem then I'll
take a look at the adjustment strategy and/or make it possible to
disable it in the kernel configuration.

 -- Keir


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