core/region: use a separate tree to check for overlaps in the subtree

[JmPotato]

What problem does this PR solve?

Issue Number: close #8136, ref #7897.

What is changed and how does it work?

Previously, removing overlapped regions in subtrees required finding overlaps for each subtree individually.
This PR introduces a separate tree specifically for checking overlaps in the subtrees, thereby reducing lookup times and improving performance.

Check List

Tests

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

> go test -timeout=30m -count=3 -benchmem -bench=BenchmarkUpdateSubTreeOrderInsensitive . > new.txt
> git checkout master #59e29cca6a0c1acb191fa50b10ca080971b2a47a
> go test -timeout=30m -count=3 -benchmem -bench=BenchmarkUpdateSubTreeOrderInsensitive . > old.txt
> benchstat old.txt new.txt
goos: darwin
goarch: arm64
pkg: github.com/tikv/pd/pkg/core
                                                                               │    old.txt    │               new.txt               │
                                                                               │    sec/op     │    sec/op     vs base               │
UpdateSubTreeOrderInsensitive/from_empty_with_size_10-8                          10.561µ ±  0%   7.258µ ±  0%  -31.28% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10-8         10.575µ ±  0%   7.293µ ±  2%  -31.04% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10-8              20.48µ ± 25%   12.68µ ± 16%  -38.09% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100-8                          269.2µ ±  1%   161.3µ ±  1%  -40.06% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100-8         272.5µ ±  2%   161.5µ ±  0%  -40.72% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100-8             328.5µ ±  7%   181.9µ ± 11%  -44.60% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000-8                         3.384m ±  2%   1.975m ±  1%  -41.65% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000-8        3.374m ±  0%   1.976m ±  1%  -41.45% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000-8            3.644m ±  4%   2.104m ±  1%  -42.27% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000-8                        36.38m ±  1%   21.01m ±  4%  -42.25% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000-8       36.41m ±  0%   21.03m ±  1%  -42.24% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000-8           38.18m ±  4%   21.93m ±  3%  -42.55% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100000-8                       372.4m ±  2%   215.7m ±  0%  -42.09% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100000-8      373.2m ±  1%   215.6m ±  0%  -42.24% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100000-8          386.4m ±  2%   226.5m ±  6%  -41.38% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000000-8                       3.874 ±  2%    2.193 ±  1%  -43.39% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000000-8      3.886 ±  1%    2.194 ±  0%  -43.53% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000000-8          3.962 ±  3%    2.252 ±  2%  -43.17% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000000-8                      46.91 ±  6%    29.19 ±  7%  -37.78% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000000-8     46.97 ±  1%    29.34 ±  2%  -37.54% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000000-8         58.87 ± 17%    36.03 ± 20%  -38.79% (p=0.002 n=6)
geomean                                                                           32.26m         19.20m        -40.49%

                                                                               │    old.txt    │               new.txt                │
                                                                               │     B/op      │     B/op       vs base               │
UpdateSubTreeOrderInsensitive/from_empty_with_size_10-8                           1600.0 ±  0%     904.0 ±  0%  -43.50% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10-8          1600.0 ±  0%     904.0 ±  0%  -43.50% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10-8             3.009Ki ± 48%   2.547Ki ± 37%        ~ (p=0.180 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100-8                         52.86Ki ±  0%   47.65Ki ±  0%   -9.87% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100-8        52.86Ki ±  0%   47.65Ki ±  0%   -9.86% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100-8            56.94Ki ± 16%   46.70Ki ± 11%  -17.99% (p=0.015 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000-8                        594.2Ki ±  0%   505.7Ki ±  0%  -14.89% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000-8       594.2Ki ±  0%   505.7Ki ±  0%  -14.89% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000-8           615.6Ki ±  5%   512.5Ki ±  6%  -16.76% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000-8                       6.001Mi ±  0%   5.020Mi ±  0%  -16.33% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000-8      6.001Mi ±  0%   5.020Mi ±  0%  -16.34% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000-8          5.960Mi ±  1%   4.979Mi ±  1%  -16.45% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100000-8                      60.37Mi ±  0%   49.59Mi ±  0%  -17.86% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100000-8     60.38Mi ±  0%   49.59Mi ±  0%  -17.86% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100000-8         60.07Mi ±  1%   49.56Mi ±  1%  -17.49% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000000-8                     600.3Mi ±  0%   495.2Mi ±  0%  -17.51% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000000-8    600.4Mi ±  0%   495.2Mi ±  0%  -17.52% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000000-8        601.9Mi ±  0%   495.8Mi ±  0%  -17.62% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000000-8                    5.879Gi ±  0%   4.844Gi ±  0%  -17.61% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000000-8   5.879Gi ±  0%   4.844Gi ±  0%  -17.61% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000000-8       5.877Gi ±  0%   4.842Gi ±  0%  -17.60% (p=0.002 n=6)
geomean                                                                          4.990Mi         4.027Mi        -19.30%

                                                                               │   old.txt    │               new.txt               │
                                                                               │  allocs/op   │  allocs/op    vs base               │
UpdateSubTreeOrderInsensitive/from_empty_with_size_10-8                          103.00 ±  0%    60.00 ±  0%  -41.75% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10-8         103.00 ±  0%    60.00 ±  0%  -41.75% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10-8              198.5 ± 26%    107.0 ± 22%  -46.10% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100-8                         2.308k ±  0%   1.392k ±  0%  -39.69% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100-8        2.308k ±  0%   1.392k ±  0%  -39.69% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100-8            2.671k ±  8%   1.419k ±  4%  -46.90% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000-8                        26.98k ±  0%   14.35k ±  0%  -46.82% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000-8       26.98k ±  0%   14.35k ±  0%  -46.82% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000-8           27.87k ±  4%   14.51k ±  2%  -47.96% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000-8                       276.5k ±  0%   145.1k ±  0%  -47.53% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000-8      276.5k ±  0%   145.1k ±  0%  -47.53% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000-8          275.9k ±  2%   144.9k ±  0%  -47.49% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_100000-8                      2.790M ±  0%   1.448M ±  0%  -48.07% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_100000-8     2.790M ±  0%   1.448M ±  0%  -48.08% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_100000-8         2.784M ±  0%   1.449M ±  0%  -47.93% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_1000000-8                     27.84M ±  0%   14.49M ±  0%  -47.95% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_1000000-8    27.84M ±  0%   14.49M ±  0%  -47.95% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_1000000-8        27.89M ±  0%   14.50M ±  0%  -48.02% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_empty_with_size_10000000-8                    278.9M ±  0%   145.0M ±  0%  -48.02% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_non-overlapped_regions_with_size_10000000-8   278.9M ±  0%   145.0M ±  0%  -48.02% (p=0.002 n=6)
UpdateSubTreeOrderInsensitive/from_overlapped_regions_with_size_10000000-8       278.9M ±  0%   145.0M ±  0%  -48.01% (p=0.002 n=6)
geomean                                                                          243.5k         130.6k        -46.36%

Release note

None.

[ti-chi-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.32%. Comparing base (644e904) to head (cfa0d7a).
Report is 1 commits behind head on master.

❗ Current head cfa0d7a differs from pull request most recent head f225511

Please upload reports for the commit f225511 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8185      +/-   ##
==========================================
- Coverage   77.40%   77.32%   -0.08%     
==========================================
  Files         471      471              
  Lines       61387    61354      -33     
==========================================
- Hits        47516    47443      -73     
- Misses      10309    10339      +30     
- Partials     3562     3572      +10     

Flag	Coverage Δ
unittests	77.32% <100.00%> (-0.08%)	⬇️

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[rleungx]

Should we use the item or something else instead of a tree?

[JmPotato]

Since there is no need to perform overlap checks on subtrees anymore, it is feasible to abandon the tree structure and adopt other simpler data structures. However, I prefer to carry out this modification separately after merging this PR due to the potentially significant changes.

[rleungx]

BTW, how much extra memory will it cost?

[JmPotato]

BTW, how much extra memory will it cost?

You can check the benchmark results in the PR description. It does not cause additional memory usage; on the contrary, it significantly reduces memory usage compared to the previous version.

[nolouch]

lgtm

[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: 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: aef4a7c

[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

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.

If you have any questions about the PR merge process, please refer to pr process.

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