# Uhd\_rx\_cfile: getting constant O-overflows using the USRP B200 with debian **URL:** \ **Category:** GNU Radio\ **Created:** [March 19, 2014, 1:44pm UTC](https://www.ruby-forum.com/t/uhd-rx-cfile-getting-constant-o-overflows-using-the-usrp-b200-with-debian/239910 "2014-03-19T13:44:33Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\ **Post date:** [March 19, 2014, 1:44pm UTC](https://www.ruby-forum.com/t/uhd-rx-cfile-getting-constant-o-overflows-using-the-usrp-b200-with-debian/239910/1 "2014-03-19T13:44:33Z")
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 ([SSDOptimization - Debian Wiki](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? ################################################## user@debian:~/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 ######################################## messung@debian:~/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 ---
**Author:** ![Ingmar\_Splitt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/ed655f/32.png) [@Ingmar\_Splitt](https://www.ruby-forum.com/u/Ingmar_Splitt)\ **Post date:** [March 19, 2014, 4:10pm UTC](https://www.ruby-forum.com/t/uhd-rx-cfile-getting-constant-o-overflows-using-the-usrp-b200-with-debian/239910/2 "2014-03-19T16:10:34Z")
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 \<