I need to write a sampling application that uses a USRP. For that, I have chosen gnuradio. I want to achieve high rates, to be able to sample bandwidths of above 200MHz.

However I have encountered a problem. The gnuradio application intermittently underperforms causing overflows. What causes this, and how can I reliably prevent it?

Usually my program runs normally, but sometimes, I don't know why, it underperforms considerably, such that it causes overflows.

I tried running the program a few times. It usually runs normally, but rarely, it starts with bad rates, and persists. I restart the script, it is fixed. There doesn't seem to be any pattern here.

So I have tried running some tests.

First, I tried a very simple program to check if the problem persists with other flowgraphs. I connected a constant source block to a probe rate, and ran the resulting python code. The problem persists. Usually when running it, it ran at around 950MHz. But when the problem starts, it runs around 570MHz.

I tried seeing if the problem occurs in a different computer. The problem persists.

I tried monitoring the CPU usage when running the code. By comparing it to when the performance is normal, the issue has a relation to the scripts CPU usage rising considerably.

In the future, I want to be able to use all available channels of the usrp, meaning that I might have even more extreme performance criteria. If overflows might be encountered during sampling due to this problem, I want to know if it is something I can fix.

I have exhausted all of my ideas with my current knowledge, and I would gladly accept any ideas or explanations. Do you think the problem is fixable with different configurations? Or maybe it is a result of how gnuradio/python works?

I am working on a very strong server, with Ubuntu20.04, and gnuradio 3.10. It is on an isolated network for security reasons, so I cannot provide any screenshots...

Thank you in advance