Uhd_rx_cfile: getting constant O-overflows using the USRP B200 with debian

Hi developers,

I have a fresh gnu radio installed with pybombs for my usrp B200. It
runs on a Lenovo X230 with debian testing x64.
When I use uhd_rx_cfile i get constant “O”-overruns (output given
below).

The uhd-benchmark runs without problems:
sudo ./benchmark_rate --duration 600 --rx_rate 32000000
So the USB3-Port isn’t the Problem. Storing in ram is also fine:
sudo ./uhd_rx_cfile -f 2445000000 --samp-rate=30000000
/tmp/test.cfile
I use a Samsung Evo 840 1TB (newest firmware) and did the
SSD-Optimizations (https://wiki.debian.org/SSDOptimization) while
searching for the error. HDPerm-, DD- and copy-benchmarks give 500mb/s
for the first seconds, later constant ~400mb/s writing speed.
Debugging with “iotop” brings (output below) 90% io-call-workload for
the benchmarks, but 0% for the uhd_rx_cfile which writes only with
240mb/s. So everything should work as expected.
Btw: I also get overruns (at a lower rate) when sampling with lower
sample rate and try to change the nice number.

Have you got any idea how to find and fix the bottleneck?

##################################################

[email protected]:~/tools/grc/target/bin$ sudo ./uhd_rx_cfile -f 2445000000
–samp-rate=30000000 /test/test.cfile -v

linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.007.000-1-ga8caec5f

– Operating over USB 3.
– Initialize CODEC control…
– Initialize Radio control…
– Performing register loopback test… pass
– Performing CODEC loopback test… pass
– Asking for clock rate 32 MHz
– Actually got clock rate 32 MHz
– Performing timer loopback test… pass

UHD Warning:
The hardware does not support the requested RX sample rate:
Target sample rate: 30.000000 MSps
Actual sample rate: 32.000000 MSps
Using mid-point gain of 36.5 ( 0.0 - 73.0 )
Motherboard: B200 (E6R04Z7B2)
Daughterboard: B200 (RX2, A:A)
Rx gain: 36.5
Rx baseband frequency: 2.445G
Rx DDC frequency: -596.046m
Rx Sample Rate: 32M
Receiving samples until Ctrl-C
Writing 32-bit complex floats
Output filename: /test/test.cfile
OOOOOOOOOOOO

#########################################

iotop

TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
171 be/4 root 3.91 K/s 0.00 B/s 0.00 % 6.63 %
[kworker/u16:3]
2656 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.04 % X :0 -auth
/var/run/lightdm~olisten tcp vt7 -novtswitch
3502 be/4 root 0.00 B/s 236.78 M/s 0.00 % 0.00 % python2
./uhd_rx_cfile -f 2~0000000 /test/test.cfile -v

########################################

[email protected]:~/tools/grc/target/bin$ sudo hdparm -tT /dev/sda

/dev/sda:
Timing cached reads: 17832 MB in 2.00 seconds = 8921.71 MB/sec
Timing buffered disk reads: 1526 MB in 3.00 seconds = 508.55 MB/sec

Hello Ingmar,

Can you please repeat the experiment with lower sampling rates (say, 10
Mhz)? Thanks.

best,
aditya

On Wed, Mar 19, 2014 at 8:42 AM, Ingmar Splitt <

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