Forum: GNU Radio Getting overflows at 50 Msps (not sure why)

E120602a851534516a3f75f6b706625e?d=identicon&s=25 Orin Lincoln (Guest)
on 2014-06-04 23:17
(Received via mailing list)
Hello,

I am trying to get samples from a B200 at 50 Msps into GNU Radio. The
UHD benchmark_rate tool receives at 50 Msps without any overflows
detected. My GNU Radio flowgraph is simply a USRP source connected to a
null sink, and I'm still getting overflows. I've tried expanding the
min_output_buffer for the USRP source, but that doesn't seem to help. I
really don't know what is causing the problem. Any suggestions about
what I should try?

Thank you,
Orin Lincoln
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2014-06-04 23:22
(Received via mailing list)
On 06/04/2014 05:16 PM, Orin Lincoln wrote:
> Thank you,
> Orin Lincoln
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
What is causing the problem is that your computer/OS simply cannot keep
up.  Gnu Radio has noticeably more overhead than a hand-crafted
   program like benchmark_rate.  Being able to maintain real-time
streaming at these rates is *challenging*, and just because
benchmark_rate
   doesn't fall over, is *zero* guarantee that some *other* program,
trying to swallow data at a similar rate, will actually be able to.

Desktop/Server operating systems (Windows, OSX, Linux, *BSD) aren't
really optimized for dealing with high-bandwidth real-time flows.
   In any given system configuration, it's rather a crap-shoot as to
whether your system will be able to keep up or not.

What type of computer do you have?  What OS?  How much memory?  Is it
the fastest memory you can use on your motherboard?



--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
Ddb503356cb90b0c95e52700445ef749?d=identicon&s=25 Tom Tsou (Guest)
on 2014-06-04 23:51
(Received via mailing list)
On Wed, Jun 4, 2014 at 5:16 PM, Orin Lincoln <orindlincoln@gatech.edu>
wrote:
> I am trying to get samples from a B200 at 50 Msps into GNU Radio. The UHD
> benchmark_rate tool receives at 50 Msps without any overflows detected. My
> GNU Radio flowgraph is simply a USRP source connected to a null sink, and
> I'm still getting overflows. I've tried expanding the min_output_buffer for
> the USRP source, but that doesn't seem to help. I really don't know what is
> causing the problem. Any suggestions about what I should try?

In addition to what Marcus said, if your application allows, you can
try 8-bit samples to relieve some pressure on the USB bus.

  -TT
95407eef371d1aa1a5696f52c8d70a0e?d=identicon&s=25 Ron Economos (Guest)
on 2014-06-05 00:44
(Received via mailing list)
On 6/4/2014 2:16 PM, Orin Lincoln wrote:
> Thank you,
> Orin Lincoln
>
On bladeRF, the number of USB3.0 buffers makes a big difference
in the maximum sample rate without overruns. On the B200, you
can try the same thing by increasing the number of buffers
in the device_addr arguments.

device_addr="recv_frame_size=65536,num_recv_frames=128,...."

Ron
E120602a851534516a3f75f6b706625e?d=identicon&s=25 Orin Lincoln (Guest)
on 2014-06-16 20:28
(Received via mailing list)
I appreciate the suggestions I received. It turns out that I was able to
run GNU Radio with realtime priority, and that solved my overflow
issues. I am now able to run flowgraphs that actually do things without
getting overflows all the time.

Thanks,
Orin Lincoln
D2595f4322a69535ddb92617d17f0eef?d=identicon&s=25 Louis Brown (madengr)
on 2014-06-16 22:24
(Received via mailing list)
Orin,

Just curious what USB 3.0 chipset and OS you are using, and if you can
go
over 50 Msps?  I am able to get 45 Msps UHD Benchmark with the VLI
VL80x,
but not over that.

Thanks,
Lou
KD4HSO




--
View this message in context:
http://gnuradio.4.n7.nabble.com/Getting-overflows-...
Sent from the GnuRadio mailing list archive at Nabble.com.
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2014-06-16 22:30
(Received via mailing list)
On 06/16/2014 04:23 PM, madengr wrote:
> Orin,
>
> Just curious what USB 3.0 chipset and OS you are using, and if you can go
> over 50 Msps?  I am able to get 45 Msps UHD Benchmark with the VLI VL80x,
> but not over that.
>
> Thanks,
> Lou
> KD4HSO
>

Also, I should point out that getting some high sample-rate in the
*benchmark* application is only a very-vague indicator of how well
things will
   do when you're actually *doing things* with the samples.  It's very
much cheaper to read samples and throw them away than it is to actually
   do things, including recording, with said samples.


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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