Chrony Local Offset Measurments
NTP Configuration
- Raspberry PI 2 (raspbian) with PPS usb gps module: Polled every 8 seconds
- AMD 64 (debian) taking time source from the Raspberry PI: Polled every 8 seconds
- This host: Mac Mini (4 core Intel i7, 16GB), MacOS 10.10.5
Graphing
- Read the 'Rem corr.' from /var/log/chrony/tracking.log
- Apply the value to a low pass filter:
mean_corr = 0.1 * (corr - mean_corr)
- Plot the result.
Assumptions
- Equal time intervals between samples in the chronyd log
(The low pass filter should probably take any interval variation into account.)
- System load on the MacOS host is constant through the test
- Ambient temperature does not vary excessively - i.e. constant drift rate
Graph Colours
| green | Offset sd |
| red | RMS Offset |
| purple | drift frequency - ppm |
| orange | lp filtered Rem. corr. |
Default Scheduling
Kernel real time scheduling disabled. 'nice' -15
Real Time Scheduling
Kernel real time scheduling enabled. 'nice' -15
