feat: add a function to get number of logical cpu cores

[Lloyd-Pottiger]

What problem does this PR solve?

Issue Number: close #4879

Problem Summary:

What is changed and how it works?

Add a function to get number of logical cpu cores:

1. Normally, $cpu = std::thread::hardware_concurrency()
2. With cgroup, $cpu = min(len(cpuset), cgroup_quota / cgroup_period)

detail doc: #4879 (comment)

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

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[Lloyd-Pottiger]

TODO:

• add unit tests (if gtest support) (Can not mock the env with different logical cpu, so delete)
• test on k8s/docker env
• support cgroup v2 limitation

[Lloyd-Pottiger]

Test on docker with --cpus=$n, the result of getNumberOfLogicalCPUCores equal to $n.
Test on WSL, the result is the same as expected.

[Lloyd-Pottiger]

/rebuild

[Lloyd-Pottiger]

/cc @JaySon-Huang @jiaqizho @ywqzzy @JinheLin

[Lloyd-Pottiger]

It does not work in some case…… I will write a doc and do more tests.

[breezewish]

Is it easy to add tests for it? How about setting up a docker, or more directly, just use cgroup in tests?

[Lloyd-Pottiger]

Is it easy to add tests for it? How about setting up a docker, or more directly, just use cgroup in tests?

Currently, I did not find the way to test by gtests. I tested manually before. (I did not test on cgroup v2 because I still could not set up the environment after trying a lot on my own machine) Do you mean run a docker in a unit test? Maybe it is hard, and is not a good way which means we may need to introduce more dependencies. However, there are some bugs indeed. I will fix later.

[Lloyd-Pottiger]

I have wrote a doc about this pr in #4879 (comment).

[Lloyd-Pottiger]

/cc @JaySon-Huang @JinheLin @jiaqizho @ywqzzy

[jiaqizho]

Can we change it to for(line by line)?

[jiaqizho]

Would you like to add some gtests to test all of functions？

You can find some example in man.

[Lloyd-Pottiger]

I will