[USRP-users] C++ thread Priority.

Marcus D. Leech patchvonbraun at gmail.com
Wed Jul 22 13:33:39 EDT 2020


On 07/22/2020 01:22 PM, David Carsenat wrote:
> Ok thanks. The code is really simple and i don't think it can be 
> optimized.
> Is there other linux OS i can try ?
> Thanks again.
>
If it's really simple, what is the sample-rate?  Is it trying to write 
data to the filesystem at high rates?  No amount of code optimization 
can get
   around the fact that the disk subsystem is very slow compared to 
other parts of the computer, like memory, CPU, etc.


> Le mer. 22 juil. 2020 à 19:12, Marcus D. Leech via USRP-users 
> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> a écrit :
>
>     On 07/22/2020 12:56 PM, David Carsenat via USRP-users wrote:
>     > Hello, I have made a c++ code which sends samples in the main
>     function
>     > and receives samples in a thread launched in this main function.
>     > I have read that we can set the real time priority with the
>     > set_thread_priority function.
>     > I have tried to call this function (with parameters (1,true) inside
>     > the main function but it doesn't seem to change the priority of the
>     > executable. When I launch another application, I have lots of U
>     and O.
>     >
>     > Do you have an idea how to achieve what I want ? i.e. allocate
>     almost
>     > all computer resources to my uhd program ? What is the best way ?
>     > I have already tuned my ubuntu with advice given on Ettus site.(
>     > cpu-freq set etc...)
>     >
>     > Many thanks
>     >
>     > David
>     >
>     In general, applications have only very-rough control over the
>     behavior
>     of the scheduler.  This is true in most general-purpose operating
>     system
>        environments, whether it's Windows, Linux, *BSD, MacOS, etc.
>
>     If you've played with priorities, and starting up other programs
>     causes
>     OU to happen, you should probably consider:
>
>     (A) Optimizing your code -- find out where the hot-spots are, and
>     see if
>     they can be improved
>     (B) Choosing a faster CPU
>
>     The CPU usage of a DSP flow is roughly proportional to:
>
>     inherent-per-sample-complexity X sample-rate
>
>     Can you lower the sample rate and still achieve what you need to
>     achieve?  Can you improve the main-path per-sample complexity?
>
>
>
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