[Discuss-gnuradio] TPB scheduler fills block buffers

[antonb]

Hi,

I am writing an application for which I want to keep the latency to a
minimum, and this involves trying to keep the buffers between the blocks as
empty as possible. Basically, I have a source block with an element size of
512 bytes that accepts data through a public member function. If there is
no data to transmit it will produce one empty packet to keep the USRP busy.
The scheduler keeps asking for 64 items and I give it one. This goes on
until its write buffer is full. The processing latency (from the source
block to the USRP) of the first items is a few ms, but this grows to well
over a second due to the large amounts of buffered data.

Looking at the behavior of the single threaded scheduler, it seems it is
trying to keep the latency low by only requesting data from source blocks
when the other blocks fail to produce anything. However, the thread per
block scheduler does not seem to care about whether a block is a source
block or not. Is there any way I can configure it to do this? Is there any
other approach for solving this problem?

Thankful for any help,
Anton Blad