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Re: [Xen-devel] what's maximum speed setting for xen network?




On Apr 23, 2005 7:31 AM,  Keir Fraser wrote:

We have no back-pressure / flow control on inter-domain networking.
This leads to embarrassing performance for UDP when the sender and
receiver share a CPU. The sender fills the receiver's buffers but
continues to send even though he drops further packets (no buffer space
at receiver) -- then the receiver gets a time slice, receives a ring's
worth of packets -- then the sender gets to run for another time slice,
most of which again is wasted -- and so on.

FWIW, I don't think this is the problem I'm running into. The reason being that I don't think the workload I'm using is heavy enough to trigger overflow. I'm sending 102 packets over the course of 2 seconds. Of these, 5 are dropped.

Assuming the ring size is given by NETIF_RX_RING_SIZE (which is defined to 256 in io/netif.h), I'm thinking that the drops can't be attributed to overflow.

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