What time did you measure, and what is the difference vs what you saw from co-sim?
There will be some overhead with the Python calls vs your co-sim time.
From memory, I think an MMIO call can be ~100MS.
(E.g. pg_ip.write() )
The call to time() will also add overhead.
If you are accessing memory (DRAM) there can be some additional (small) variability.
Cathal