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xen-devel
Re: [Xen-devel] what's maximum speed setting for xen network?
On 22 Apr 2005, at 20:53, mukesh agrawal wrote:
I've got a configuration with DomU talking to Dom0 over a vif, and
seem to be seeing UDP losses, even at low data rates. (I haven't dug
into this deeply to very the problem yet, though.) So I'd be
interested if you're seeing something similar.
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.
We need a sensible mechanism for ensuring batched packet delivery, but
also to ensure that comms rings do not so easily get overflowed. This
would vastly improve the inter-domain performance, far more than
striving for zero copy or other such tweaks.
It would be great if someone else is interested in investigating this.
:-)
-- Keir
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