Hotplugged CPUs are not rounded up

[gkhanna79]

Description of problem

Assume we use the following values of cpu_quota and cpu_period to influence hotplugged vCPU count for a POD:

cpu_quota = 170000
cpu_period = 100000

Using the formula described here, the computed value is 2.69. Per this, the computed value will be rounded up to 3.

However, the documentation here does not make a reference to the rounding up.

Expected result

If a POD contains 1 container, it would be expected that 3 vCPUs will be hotplugged (excluding the default 1 vCPU).

If a POD contains two containers, it would be expected 3 vCPUs to be hotplugged (excluding the default 1 vCPU) for each container.

Actual result

In each POD, we observe 2 vCPUs to be hotplugged per Container though, per documentation, POD1 should have gotten 4 (including the 1 default vCPU) and POD2 should have gotten 7 (also including the 1 default vCPU).

It appears that this behavior maybe due to uint casting done here.

[gkhanna79]

@egernst Filing per our offline discussion.

[egernst]

Thanks @gkhanna79

@devimc - any chance you can take a look? We have unit tests for this flow, but it is specific to Kubernetes based resource requests. I'd like to be able to

[egernst]

Hey @gkhanna79 - the logic is correct. The document is wrong:
vCPU = Quota/Period. mCPU = Quota/Period * 1000

I'll open an issue in the docs repo to get this fixed...

[gkhanna79]

Thanks for the confirmation @egernst. It makes everything sound reasonable now :)

[egernst]

@gkennedy12 -- closing this issue - let's track in error in vCPU calculation documentation #489

Thanks,
Eric