Automatically set GOMAXPROCS according to linux container cpu quota

[drwatsno]

Is your feature request related to a problem? Please describe.

As you know, in Go 1.5, GOMAXPROCS is automatically set to number of cpus. This does not take into account the CPU quotas allocated to the container through the cgroups, and this leads to serious throttling of the process.

More context:
https://medium.com/omio-engineering/cpu-limits-and-aggressive-throttling-in-kubernetes-c5b20bd8a718

Describe the solution you'd like

Possible solution:

1. ADD CGROUPS_V1_AUTO_MAX_PROCS_ENABLED option. Defaults to false
2. If true, set GOMAXPROCS automatically according to cpu quota

Describe alternatives you've considered

There are several ways to fix this:

1. Install GOMAXPROCS manually via env variables.
2. Wait until the problem is solved in Go itself, and do nothing runtime: make GOMAXPROCS cfs-aware on GOOS=linux golang/go#33803
3. Set GOMAXPROCS automatically using cgroups hierarchy

The first solution is not optimal, since every time you change the limits and requests, you will need to independently calculate and set the value for GOMAXPROCS.
The second solution is rather naive - we need some kind of temporary solution now
The third solution may be a compromise, but in this case this feature should be disabled by default (since there may be cgroups v2, which is currently not supported by automaxprocs library)

Additional context

This library can help
https://github.com/uber-go/automaxprocs

[aeneasr]

Sounds like a good idea! Contributions welcomed :)