Re: [Discuss-gnuradio] To implement WiMAX with GnuRadio or not?

[Alexander Chemeris]

On Sat, May 28, 2011 at 19:38, Michael Dickens <address@hidden> wrote:
> On May 28, 2011, at 11:26 AM, Alexander Chemeris wrote:
>> 5) How well is GnuRadio suited for real-time operation?
>
> In a general sense, yes, GNU Radio is well suited for real-time signal 
> processing of data streams.  That said: "Real time" is only meaningful 
> knowing the performance criteria.  What sort of performance do you require 
> processing for?

Real-time is not about performance, but about predictability ;)
I have to be sure that my flowgraph always executes before the
deadline is hit. So everything that introduces jitter is a no-no.

>> 5.1) Specifically - is memory allocated from heap with malloc() or it
>> supports non-blocking memory pools?
>
> IIRC (Tom? Eric?): GNU Radio uses the standard C++ "new" command for most 
> memory allocations -- and thus it is memory from the heap.  One can always 
> overload this method globally or locally if required, to provide memory from 
> pools or other means.

Is this "new" called during the flowgraph execution loop? It's too
bad, if it is. Standard memory allocation schemes introduce random
delays in a thread execution. And implementation of a lock-free memory
allocator is a complex task. We used memory pools instead, but this
requires special care - you can't replace a "new" with memory pool
get() with a regexp.

>> 5.2) Can the whole flowgraph be executed from a single thread to
>> minimize cross-thread communication overhead (and jitter)?
>
> Yes.  Your choices are a single thread for all or 1 thread per block. - MLD

Great.

-- 
Regards,
Alexander Chemeris.