Re: [Discuss-gnuradio] TPB Scheduler - Block Scheduling Rate

[Michael Dickens]

On Jan 28, 2011, at 2:23 PM, Ben Hilburn wrote:
> As I understand it, there is code in the GNURadio scheduler stuff that
> manages block scheduling, to some degree.
> 
> I'm aware of the kernel's role in switching between the threads
> themselves, but I was under the impression that block scheduling, was
> at least in some part, influenced by GNU Radio.
> 
> If this is incorrect though, someone please correct me!

Yes, this is true, Ben.  The OS handles the basics of thread execution, but the 
TPB scheduler does handle "when" a block's "general_work" method is actually 
called.  See gnuradio-core/src/lib/runtime, files "gr_tpb_thread_body.cc" 
(which for the most part is a simple loop calling the block executor and 
neighbor blocks when things change) and "gr_block_executor.cc" (which is where 
the meat of what you're looking for it, I believe).  For the latter, you can 
set ENABLE_LOGGING to 1, which should give you an idea of what the "decision 
process" is.

I think the general idea goes roughly like this: When data in a given buffer 
changes (whether through generated or consumed items), each block that is 
associated with that buffer checks to see if there is "enough" input data and 
output buffer space for a "reasonable sized" computation.  If not, then go back 
and wait for buffers to change; if so, then do the computation (call 
"general_work").  You'll need to look through the code to determine what 
"enough" and "reasonable sized" mean -- looking at the debug log might help as 
well.

It's been a long time since I've thought about these algorithms, so hopefully 
the above is reasonably correct.  And, I hope this helps! - MLD