*: add the http api and new configuration members for ballast object

[hnes]

What problem does this PR solve?

Problem Summary:

Try to reduce the GC frequency on some occasions.

What is changed and how it works?

What's Changed:

Add a ballast object.

How it Works:

Here are some articles and documentation.

SetGCPercent

Go memory ballast: How I learned to stop worrying and love the heap

proposal: runtime: add a mechanism for specifying a minimum target heap size

Performance Benefits

In a typical OLTP scenario, 2GB ballast could bring tps ~+16.8%, latency ~-13.5%, cpu ~-16.3%.

Check List

Tests

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

# get current size of the ballast object
curl -v 127.0.0.1:10080/debug/ballast-object-sz
# reset the size of the ballast object (2GB in this example)
curl -v -d "2147483648" -X POST 127.0.0.1:10080/debug/ballast-object-sz

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

Add the http api and new configuration members for the ballast object.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• coocood
• youjiali1995

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[coocood]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b31be95