Storage: Avoid wasting CPU with inefficient scheduling in SegmentReadTaskScheduler

[JinheLin]

What problem does this PR solve?

Issue Number: close #6495

Problem Summary:

What is changed and how it works?

To determine whether a SegmentReadTaskPool needs to be scheduled, we need to determine free block slots and free active segments both greater than 0.

Check List

Tests

• Unit test

• Integration test

• Manual test (add detailed scripts or steps below)
  Before this PR:
  
  After this PR:
  

• 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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JaySon-Huang
• Lloyd-Pottiger

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[JinheLin]

/run-all-tests

[JinheLin]

/run-all-tests

[Lloyd-Pottiger]

Others LGTM.

[sre-bot]

All committers have signed the CLA.

[JinheLin]

/run-all-tests

[JinheLin]

/run-integration-test

[JinheLin]

/run-unit-test

[JinheLin]

/merge

[ti-chi-bot]

@JinheLin: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

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

Commit hash: 5e488cf

[ti-chi-bot]

@JinheLin: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

trigger some heavy tests which will not run always when PR updated.

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #6634.