globalsort: fix stuck when ingesting small kv

[D3Hunter]

What problem does this PR solve?

Issue Number: close #62388

Problem Summary:

What changed and how does it work?

consider the memory taken by slice header when splitting range

Check List

Tests

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

same case in the issue, before this pr, 2 out of 3 runs stuck. after this pr, we run 10 times, all success.

• No need to test

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @D3Hunter. Thanks for your PR.

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[Benjamin2037]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.8131%. Comparing base (0c6cbc1) to head (8cdc3b7).
Report is 11 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #62407        +/-   ##
================================================
+ Coverage   72.9071%   73.8131%   +0.9060%     
================================================
  Files          1754       1785        +31     
  Lines        484998     497265     +12267     
================================================
+ Hits         353598     367047     +13449     
+ Misses       109767     107843      -1924     
- Partials      21633      22375       +742     

Flag	Coverage Δ
integration	45.3764% <0.0000%> (?)
unit	72.3016% <100.0000%> (+0.1306%)	⬆️

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

Components	Coverage Δ
dumpling	52.6673% <ø> (-0.1132%)	⬇️
parser	∅ <ø> (∅)
br	46.3605% <ø> (+0.0639%)	⬆️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, joechenrh

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Details

Needs approval from an approver in each of these files:

• pkg/lightning/OWNERS [Benjamin2037]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-07-15 02:23:52.205530249 +0000 UTC m=+2571284.928709231: ☑️ agreed by Benjamin2037.
• 2025-07-15 02:52:29.975305442 +0000 UTC m=+2573002.698484423: ☑️ agreed by joechenrh.

[Benjamin2037]

/retest

[Benjamin2037]

/retest

[tiprow]

@D3Hunter: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
fast_test_tiprow	8cdc3b7	link	true	/test fast_test_tiprow

Full PR test history. Your PR dashboard.

Details

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 kubernetes-sigs/prow repository. I understand the commands that are listed here.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #62409.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #62410.
But this PR has conflicts, please resolve them!