[USRP-users] C++ thread Priority.

Marcus D. Leech patchvonbraun at gmail.com
Wed Jul 22 13:46:36 EDT 2020


On 07/22/2020 01:40 PM, David Carsenat wrote:
> It just put received samples in a circular buffer and  transmit this 
> buffer. A delay line.
> But the SR is 50 Msps... 8 bits.
>  Do you have ideas about OS ?
> Thanks.
>
There are commercial real-time low-latency OS "out there" that aren't 
free, and UHD has not been ported to them as far as I know.


> Le mer. 22 juil. 2020 à 19:33, Marcus D. Leech 
> <patchvonbraun at gmail.com <mailto:patchvonbraun at gmail.com>> a écrit :
>
>     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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>>
>

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