schedule: tune waiting region length

[disksing]

Signed-off-by: disksing [email protected]

What problem does this PR solve?

The regions in the waring list are checked every tick. When there are many regions need to fix, it costs too much CPU.

Part of #3744

What is changed and how it works?

Update cache size to a smaller value.

Check List

Tests

• Unit test

Release note

None

[rleungx]

IMO, if the cache size is small, it will be less useful when there are a lot of regions.

[disksing]

IMO, if the cache size is small, it will be less useful when there are a lot of regions.

The problem is that for every tick we only scan 128 regions. This means that when the 1000 length cache is filled, we will spend 90% of our CPU time repeatedly checking the region in the cache and only 10% of our CPU time on the scan. This doesn't seem quite suitable anymore.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.