This is a docker image intended to print out available processors and max memory of java runtime, in order to visualize cpu/memory requests/limits specified on pod in kubernetes.
Tested with docker image openjdk:8-jre on a kubernetes cluster of 3 VMs with 16 vCPU and 32 GiB memory. Memory request and limit are not set. Test files can be found under tests directory.
| CPU Request | CPU Limit | = | Available Processors | Max Memory |
|---|---|---|---|---|
| 0 / (none) | (none) | = | 1 | 8151564288 |
| 500m | (none) | = | 1 | 8151564288 |
| 1 | (none) | = | 16 | 7495745536 |
| 1500m | (none) | = | 2 | 7495745536 |
| 2 | (none) | = | 2 | 7495745536 |
| 500m | 800m | = | 1 | 8151564288 |
| 500m | 1 | = | 1 | 8151564288 |
| 1 | 2 | = | 2 | 7495745536 |
| 1 | 3500m | = | 4 | 7495745536 |
| 1500m | 3500m | = | 4 | 7495745536 |
Conclusions:
- If CPU limit is specified, available processors are set to the ceiling of CPU limit;
- If CPU request is specified but limit unspecified, available processors are set to the ceiling of CPU request with the following exception:
- If CPU request is set to 1, available processors are set to the number of CPU cores of the underlying VM.