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Re: perle jetstream settings

Marion Hakanson hakansom@ohsu.edu
Mon, 14 Aug 2006 13:05:28 -0700 (PDT)

david.k.harris@siemens.com said:
>   If you have bursty traffic, it sounds like it's the JetStream, based on
> what you have said. (You indicated that the Rack+ doesn't exhibit the symptom
> when connected to the same serial ports, if I understand you correctly.)

Yes, both units are connected to the LOM ports on identical Sun V120's.

>   You may find a serial setting, but it may also be that the CPU of the
> JetStream can't keep up with the high rates during prolonged bursts. Another
> option is that the serial rate may be too slow, and the CPU is time-slicing
> to check all of the other ports before getting back to the next batch from
> the busy port(s).

We're running at the V120 default serial settings 9600bps, 8/N/1, no flow
control running at all.  Haven't seen signs of lost characters, so the
"CPU too slow" scenario seems unlikely, especially at these speeds.

>   If the higher data rate works, it may indicate that the JetStream has an
> issue polling the various ports. This could point to an issue handling the
> interrupts from the UARTs, or servicing a busy network interface. (Are you
> attaching the JetStream to a switch port, or a busy hub?) 

Nothing's busy yet;  Just one serial port for testing so far, and it's
a switched 10/100 network with not much going on.

When I asked about tuning, I was wondering if there wasn't a poll-type
setting which could be changed.  Given the low-speed nature of this
environment, going to a more interrupt-driven scenario in order to get
smoother output would be an acceptable trade-off.

Cabling, adapters, and V120's are capable of doing CTS/RTS flow control,
so I'll see about trying higher port speeds to see if things go a little
more smoothly.  Maybe with flow-control enabled the JetStream will use a
different algorithm, or as you said, the faster baud rate may just make it
work harder and/or poll faster.

Thanks and regards,