On Sat, Sep 04, 2010 at 08:22:38PM -0400, Marcus D. Leech wrote: > On 09/04/2010 08:08 PM, Tom Rondeau wrote: > > On Sat, Sep 4, 2010 at 12:19 AM, Marcus D. Leech <mle...@ripnet.com> wrote > > > > Like Eric said, remove the throttle or at least change the rate and > > that should clean things up. > > > > Tom > > > > > I also noted in the reply to Eric that I observe the same behaviour with > an external source that is producing 4800 symbols/second--so > it's not the throttle *per se*, but rather the way that work "chunks" > get scheduled in Gnu Radio. With a "fast" source, you dont find yourself > in a situation where there aren't enough "chunks" to keep things busy. > > But a very reasonable example would be something like a cross-band > digital repeater application, where bits/symbols would be arriving > at the "channel rate", and need to leave the Tx in something at least > approaching real time--you certainly need to have a bit of > elastic buffering to compensate for clock-skew between the two sides, > but several-tens-of-seconds of latency isn't likely to be very > useful in the real world. > > Note that I'm not criticizing anybody or anything. I'm making > observations, and I *do* understand *why* it is the way it is. > My little test flow-graph failed the "least astonishment test", which > is why I felt I needed to comment. > > Would it be reasonable to open a discussion about this class of > flow-graph? I think they can be characterized as flow-graphs with > a low symbol rate, and high interpolation (which I think is where the > buffer-multiplier effect may be coming into play). In such flow-graphs, > would it be reasonable to be able to "tweak" the scheduler to deal > with this type of situation? I have little insight into how the scheduler > works in detail, but I think I understand the "fits and starts" that I > was observing. > > So, is this a reasonable discussion topic? Are other folks working on > "stuff" that will run into part of the performance diagram I ran > into yesterday? Or is everyone else working on high-event-rate type > signal chains?
Marcus, This is certainly a reasonable discussion topic. I suggest before wading in that you first enable the scheduler logging that I mentioned in a prior post and take a look at that. Feel free to send me the logs too. What we're looking for is which block is forcing the large chunk size. If you were reading from a file using for example gr.file_source, it won't return until until it's completely filled up the downstream buffer given to it. That's just how it's written. A trivial change would be to have it loop until it it read min(N_USER_SPECIFIED_ITEMS, noutput_items) items. Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
