Re: dev.bce.X.com_no_buffers increasing and packet loss

"David Christensen" wrote:
> > Yeah, but the question is why bce(4) has no available RX buffers.
> > The system has a lot of available mbufs so I don't see the=20
> > root cause here.
> 
> What's the traffic look like?  Jumbo, standard, short frames?  Any=20
> good ideas on profiling the code?  I haven't figured out how to use
> the CPU TSC but there is a free running timer on the device that
> might be usable to calculate where the driver's time is spent.

It looks like the traffic that provoked it was this:

10:18:42.319370 IP X.4569 > X.4569: UDP, length 12
10:18:42.319402 IP X.4569 > X.4569: UDP, length 12
10:18:42.319438 IP X.4569 > X.4569: UDP, length 12
10:18:42.319484 IP X.4569 > X.4569: UDP, length 12
10:18:42.319517 IP X.4569 > X.4569: UDP, length 12

A flurry of UDP tinygrams on an IAX2 trunk.  The packet rate isn't
spectacular at about 30kpps which on top of the base load of 60kpps
still isn't a fantastic packet rate.  The interesting thing is that
while this storm was inprogress, it almost entirely excluded other
traffic on the network.

There have been reports of backplane congestion on the switches we
use when UDP packets smaller than 400 bytes arrive within 40us of
eachother.  But that still doesn't explain the counter increases
and high interrupt CPU usage, unless the switch was producing garbage
output in response.

Ian

--
Ian Freislich