Re: [Discuss-gnuradio] Gigabit Ethernet cards

[Marcus D. Leech]

On 07/05/2010 12:33 PM, Josh Blum wrote:
> I can think of a nicer way to print the error messages SX, but dropped
> packets are a fact of life; especially running at 25 Msps.
>
> On my linux box, running benchmark at full rate, i usually see a few
> dropped packets initially and at the end when it finishes.
>
> AMD Athlon(tm) II X4 620 Processor
> Realtek Semiconductor Co., Ltd. RTL-8169 Gigabit Ethernet (rev 10)
>
>   
I see dropped packets at much lower bandwidths, but with more complex
flow-graphs.  But the puzzling
  thing is the CPU isn't even close to 100% when I see these.

On my 6-core Phenom II X6 1090T with 8G of 1333 DDR3 with the CPUs
hard-configured to run at 3.2GHz,
  I can run usrp2_fft.py at 25Msps, and get the occasional dropped
packet, but I can't run
  more-complex flow-graphs beyond about 8Msps without it getting into
serious droppage, even
  without 100% CPU utilization.

This is with an RTL ethernet chip on the mobo.  I've been told that
Intel e1000e cards do somewhat better--
  perhaps deeper FIFOs or something like that.

I know that for the project I just left, I was doing a device driver for
a Xilinx-TEMAC with a proprietary buffer
  manager in the FPGA--it had a FIFO depth of only 8, which caused a lot
of heartache for bursts of
  closely-spaced packets, and a USRP2 runnning "full bore" would almost
certainly have caused it
  really bad heartburn :-)


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