[USRP-users] C++ thread Priority.

Luke Whittlesey luke.whittlesey at gmail.com
Thu Jul 23 14:24:41 EDT 2020


You might try nice : https://en.wikipedia.org/wiki/Nice_%28Unix%29

On Thu, Jul 23, 2020 at 1:13 PM David Carsenat <carsenat at gmail.com> wrote:
>
> Many thanks but I am already in O3.
>
> Le jeu. 23 juil. 2020 à 15:46, Luke Whittlesey via USRP-users <usrp-users at lists.ettus.com> a écrit :
>>
>> This is probably not the issue, but sometimes I forget to turn the
>> compiler optimizations on and that can give you a little boost
>> depending on the code. gcc -O2 ...
>>
>> On Wed, Jul 22, 2020 at 4:20 PM Marcus D. Leech via USRP-users
>> <usrp-users at lists.ettus.com> wrote:
>> >
>> > On 07/22/2020 03:18 PM, Rob Kossler wrote:
>> >
>> > If you are using X310 or N310, you might try DPDK. Even though it is a pain, it would be a whole lot easier than trying a new OS, I believe.  Using DPDK enabled my application (which was storing Rx samples to SSD) to run a bunch faster than without DPDK.
>> >
>> > Thanks, Rob.  DPDK does facilitate lower-cost higher data transfer into the application.  That may, or may not, be the issue here.
>> >
>> >
>> >
>> > On Wed, Jul 22, 2020 at 1:47 PM Marcus D. Leech via USRP-users <usrp-users at lists.ettus.com> wrote:
>> >>
>> >> 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> 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> 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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