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Re: [Discuss-gnuradio] Understanding USRP2 flow control

From: OE1RSA
Subject: Re: [Discuss-gnuradio] Understanding USRP2 flow control
Date: Tue, 20 Jul 2010 10:24:51 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20100527 Lightning/1.0b1 Thunderbird/3.0.5

Thank you for your answer.

Am 2010-07-19 22:06, schrieb Eric Blossom:
> Flow control is handled at the link level using ethernet PAUSE frames.

I was not aware of this ethernet "feature". Having learned
something new.

> Be sure to enable real-time scheduling by calling
>     if gr.enable_realtime_scheduling() != gr.RT_OK:
>         print "Note: failed to enable realtime scheduling, continuing"
> before starting or running the flow graph.
> If you haven't already, ensure that /etc/security/limits.conf contains
> this line:
> @usrp          -       rtprio          50
> and that you are a member of group "usrp".

Made everyting as told, but still no success.

Another observation I have made:

I am using two kernels from the ubuntu 10.04 LTS distro:

2.6.32 generic and
2.6.31 rt

It is interesting that the generic kernel does better than
the rt kernel. I.e. the rt is practically unusable at
interpolation 4. The generic does quite well for a while,
then suddenly drops off.

Btw.: I am using the e1000e driver for intel cards.

Possibly it may be an issue with the driver?

Do you have an idea how I could find out whether my
problems are because of buffer overrun or underrun?

Regards Roland

  _  _  | Roland Schwarz OE1RSA
 |_)(_  | sip:address@hidden
 | \__) | mailto:address@hidden
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