Re: Tag Best Practices & Performance?

[Jeff Long]

See:

https://wiki.gnuradio.org/index.php/Tagged_Stream_Blocks

https://wiki.gnuradio.org/index.php/Stream_Tags

It's a little confusing at first that they're called Stream Tags and Tagged Streams.

On Tue, Nov 24, 2020 at 11:35 AM Jeff Long <willcode4@gmail.com> wrote:

A tag is a piece of metadata that points to a specific sample in a stream. Tagged streams operate on chunks of samples, using a certain tag to determine the chunk length. Streams are simpler to deal with, unless you need data chunked.

What kind of performance issues are you finding?

If you are implementing a block, and do not want tags passed through, `set_tag_propagation_policy(TPP_DONT)`.

On Mon, Nov 23, 2020 at 3:55 PM Nicholas Long <nicholaslong94@gmail.com> wrote:

Hi, So I am not sure exactly how to ask this, but I have a few questions about tag best practices when creating OOT modules, apologies if this is answered elsewhere...

What is the main source of performance issues with tag propagation: Is it primarily copying overhead? Are there contention issues? or is most of the overhead in the actual reading/setting of tags? I guess part of my question is how are tags passed between blocks, I understand the ring buffers, but tags are still somewhat a mystery to me.

Are tagged stream blocks better than just a stream with tags? From my limited ability to parse tagged stream blocks seem to limit the number of calls to get_tags_in_range, but they still pass on all other tags on the input buffer to the output buffer regardless. 

Thanks, 

Nick