scheduler: enlarge the search space so that the hot-scheduler can still schedule under dimensional conflicts

[lhy1024]

What problem does this PR solve?

Issue Number: Ref #4949

What is changed and how does it work?

1. enlarge the search space so that the hot-scheduler can still schedule under dimensional conflicts
2. Introduce stddev to reduce unnecessary scheduling

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

master

master with close strcit-pick

pr

Release note

enlarge the search space so that the hot-scheduler can still schedule under dimensional conflicts

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[REVIEW NOTIFICATION]

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• HunDunDM
• nolouch

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[nolouch]

/merge

[ti-chi-bot]

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

/run-all-tests

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[ti-chi-bot]

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

Commit hash: 30d3196

[codecov]

Codecov Report

Merging #4912 (1db24bf) into master (1f3c305) will increase coverage by 0.21%.
The diff coverage is 100.00%.

❗ Current head 1db24bf differs from pull request most recent head 1155fd6. Consider uploading reports for the commit 1155fd6 to get more accurate results

@@            Coverage Diff             @@
##           master    #4912      +/-   ##
==========================================
+ Coverage   75.40%   75.62%   +0.21%     
==========================================
  Files         308      308              
  Lines       30484    30498      +14     
==========================================
+ Hits        22987    23064      +77     
+ Misses       5491     5449      -42     
+ Partials     2006     1985      -21     

Flag	Coverage Δ
unittests	75.62% <100.00%> (+0.21%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/schedulers/hot_region.go	83.52% <100.00%> (+0.19%)	⬆️
server/statistics/store_hot_peers_infos.go	100.00% <100.00%> (ø)
server/statistics/store_load.go	95.79% <100.00%> (+0.03%)	⬆️
pkg/cache/cache.go	53.57% <0.00%> (-10.72%)	⬇️
server/schedule/hbstream/heartbeat_streams.go	72.72% <0.00%> (-9.10%)	⬇️
server/schedulers/evict_leader.go	78.82% <0.00%> (-0.91%)	⬇️
server/config/persist_options.go	93.09% <0.00%> (-0.73%)	⬇️
server/schedule/checker/rule_checker.go	79.18% <0.00%> (-0.72%)	⬇️
server/schedule/checker/checker_controller.go	77.50% <0.00%> (-0.55%)	⬇️
server/server.go	72.53% <0.00%> (-0.28%)	⬇️
... and 21 more

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[nolouch]

/merge

[ti-chi-bot]

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

/run-all-tests

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]

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

Commit hash: 1db24bf