[USRP-users] Retuning time explodes over time

Dario Fertonani dario.fertonani at gmail.com
Thu Oct 8 02:17:59 EDT 2015

Findings below are for B210, UHD 3.9.1, Ubuntu 14.04.3, x86 CPUs.
All machines show the same problem (Broadwell NUC, Haswell PC).

In my LTE app, which needs to retune rx frequency every few tens of
seconds, the retuning time slowly increases, to the point where it is too
slow (after several hours).
I was able to replicate this behavior in a toy test (attached), so that the
problem is seen over a few minutes instead of several hours. The retuning
time explodes pretty quickly (figure attached). Also, the CPU usage does
the same, which is not expected, especially in this toy test that does
nothing but retuning (not even streaming).

For those interested in replicating the problem, the attached code is
compiled with

g++ retuneTest.cpp -o retuneTest -std=c++11 -O3 -luhd

and run with

./retuneTest 1728 739 > /dev/null 2> retuneTest.log

to store results to file retuneTest.log. The following octave line may be
used to plot:

x = load( 'retuneTest.log' ); plot( cumsum( x( : , 3 ) )*1e-3 , x( : , 3 )
, 'LineWidth' , 2 ); grid on; ylabel( 'Retuning time [ms]' ); xlabel(
'Board time [s]' );

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