Allow specifying static buffer/overhead for MAXPROCS

[DerekTBrown]

Context

• We have observed that setting GOMAXPROCS=cpu.limits leads to some low level of CPU throttling because there are other processes not accounted for. It seems others have observed this case as well. ¹
• We also have a few systems that fork non-golang procs within the same CPU namespace.
• We would like a mechanism to reserve some headroom for MAXPROCS (i.e. subtract some fixed constant from the value set by automaxprocs).

Feature Request

• Support an environment variable like AUTOMAXPROCSBUFFER=2 that is subtracted from the observed CPU limit before setting GOMAXPROCS

Footnotes

1. https://news.ycombinator.com/item?id=42248550 ↩