Expose cpu quota

[ovesh]

This PR exposes the api for querying the cpu quota.

The specific use case is when we need to specify the concurrency level (via cli arg) for a non-golang subprocess.

[codecov]

Codecov Report

Merging #28 into master will decrease coverage by 1.82%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #28      +/-   ##
==========================================
- Coverage   91.91%   90.09%   -1.83%     
==========================================
  Files           8        9       +1     
  Lines         198      202       +4     
==========================================
  Hits          182      182              
- Misses         13       17       +4     
  Partials        3        3              

Impacted Files	Coverage Δ
cpuquota/cpuquota.go	0.00% <0.00%> (ø)

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[jcorbin]

Would your use case be able to instead just use runtime.GOMAXPROCS(-1) to get the effective value separately from this library?

[ovesh]

Would your use case be able to instead just use runtime.GOMAXPROCS(-1) to get the effective value separately from this library?

@jcorbin
To my understanding, no. runtime.GOMAXPROCS(-1) won't return an accurate CPU allocation for a containerized application. It returns the global runtime.gomaxprocs, which I verified is the total number of cores on the host and not the CPU allocation.

Am I misunderstanding your comment?

[jcorbin]

Would your use case be able to instead just use runtime.GOMAXPROCS(-1) to get the effective value separately from this library?

@jcorbin
To my understanding, no. runtime.GOMAXPROCS(-1) won't return an accurate CPU allocation for a containerized application. It returns the global runtime.gomaxprocs, which I verified is the total number of cores on the host and not the CPU allocation.

Am I misunderstanding your comment?

So our automaxprocs library works be changing that value. Any time after that, you'll get the newly affected value ( unless something else has changed it of course, which should be rare ). It adds a little bit of logic like "round down" and minimum clamping. But it will be better than the total number of cores available.

[ovesh]

So our automaxprocs library works be changing that value

I'd like to get the value without setting it for the current process.

[CLAassistant]

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[piyush-singh]

This PR would resolve #29 which would be useful for us here at cockroach. Any chance we can revive this?

[prashantv]

Please see my comment here: #29 (comment)