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Re: [Discuss-gnuradio] [USRP-users] Reliable Ethernet controllers and la

From: Ian Buckley
Subject: Re: [Discuss-gnuradio] [USRP-users] Reliable Ethernet controllers and laptops for USRP N210 ?
Date: Tue, 11 Dec 2012 23:17:31 -0800

I ran benchmark_rate with the same parameters tonight on an Intel 82574L and and Intel 82579V, also with flawless results. 

On Dec 11, 2012, at 12:53 PM, Balint Seeber <address@hidden> wrote:

Hi Richard,

Thanks for reporting on your experiments! I have doing a few lately myself (specifically in regards to USRP latency).

I have a Thinkpad T430s with a 82579LM. The benchmark_rate reports zero underflows/overflows for unidirectional streaming. Bi-directional results in some TX underflows with the default MTU, however increasing this results in no underflows, e.g.

sudo ifconfig eth0 mtu 9000

sudo /usr/local/share/uhd/examples/benchmark_rate --rx_rate 25e6 --tx_rate 25e6 --duration 30 --args="recv_frame_size=3792,send_frame_size=3792"

Remember the 'sudo' will help by enabling 'real-time' (SCHED_FIFO) scheduling in the Linux kernel.

Benchmark rate summary:
  Num received samples:    749991475
  Num dropped samples:     0
  Num overflows detected:  0
  Num transmitted samples: 749969786
  Num sequence errors:     0
  Num underflows detected: 0

I have found a number of parameters can be tweaked to change general N-series communication behaviour with the Intel NIC (specifically interrupt moderation, MTU [above], etc):

sudo modprobe -r e1000e
sudo modprobe e1000e debug=16 InterruptThrottleRate=0 TxAbsIntDelay=0 TxIntDelay=0 RxAbsIntDelay=0 RxIntDelay=0

Changing CPU governor to 'performance' on all cores may also help in certain situations.

Please take a look at this document I've been putting together for more details: http://code.ettus.com/redmine/ettus/projects/public/wiki/Latency

Let us know if any of the above tips improve your results.

Hope that helps,

On Tue, Dec 11, 2012 at 8:26 AM, Rickard Radio <address@hidden> wrote:
OK, I just tried this on a colleagues brand new Thinkpad T430s and it works without any packet drops or other Ethernet problems on that laptop (at least for a minute or so). It has the Intel 82579LM Ethernet chip so that chip doesn't seem too bad after all (like the Artheros 8151 which I have problems with).


On Dec 11, 2012, at 12:51 PM, Rickard Radio <address@hidden> wrote:

Hi all,

Can anyone please try this on a laptop, preferably a Lenovo Thinkpad, with a N210 and report what you get:
"/uhd/examples/benchmark_rate --rx_rate 25e6"


On Dec 7, 2012, at 3:32 PM, Rickard <address@hidden> wrote:

I wonder which GigE controllers (manufacturer & versions) and laptop computers are working hassle free, without dropping packets etc., at the highest sampling rates with the USRP N210 which results in 800 Mbit/s raw data (or about 835 Mbit/s total UDP) ?!  

Please test your laptop with  "/uhd/examples/benchmark_rate --rx_rate 25e6" or "uhd_fft -s 25e6"  and report your findings!

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