[leni536]

I'm not familiar with udb, only with rr. Compared to rr, gdb's recording for reversible debugging is tremendously slower. However rr has strict requirements for the CPU (didn't work on AMD, the last time I looked) and requires some permissive perf_event_paranoid setting to run.

In my experience rr's recording is around x2 slower for single threaded programs than running the program on its own.

I think featurewise they are in parity.

I heard that udb is like rr, but better on some fronts (except price and software freedom).