fix: increase tipset cache size

[hanabi1224]

Summary of changes

Changes introduced in this pull request:

Reference issue to close (if applicable)

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Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• Chores
  • Increased the default chain tipset cache capacity, resulting in improved runtime performance and memory efficiency for chain storage operations.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 890dacc3-6354-4d50-9cbc-29128d499431

📥 Commits

Reviewing files that changed from the base of the PR and between af2988e and fcd20d7.

📒 Files selected for processing (1)

• src/chain/store/index.rs

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• filecoin-project/lotus (manual)

🚧 Files skipped from review as they are similar to previous changes (1)

• src/chain/store/index.rs

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Walkthrough

The PR triples the default tipset cache capacity used by ChainIndex by changing DEFAULT_TIPSET_CACHE_SIZE from 2880 to 8640 entries in src/chain/store/index.rs.

Changes

Tipset Cache Capacity

Layer / File(s)	Summary
Tipset cache size constant src/chain/store/index.rs	DEFAULT_TIPSET_CACHE_SIZE constant multiplied by 3 (from nonzero!(2880_usize) to nonzero!(2880_usize * 3)), increasing the default tipset cache capacity used by ChainIndex::new.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• ChainSafe/forest#6880: Also modifies cache-related configuration in src/chain/store/index.rs, adjusting tipset and height caching capacity and usage.
• ChainSafe/forest#7112: Related work on tipset_by_height caching behavior in the same ChainIndex cache area.
• ChainSafe/forest#7126: Adjusts default tipset cache sizing constants affecting related caching behavior.

Suggested reviewers

• LesnyRumcajs
• akaladarshi

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: increase tipset cache size' is directly related to the main change—increasing DEFAULT_TIPSET_CACHE_SIZE from 2880 to 8640.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch hm/increase-tipset-cache-size

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch hm/increase-tipset-cache-size

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.34%. Comparing base (be7fba3) to head (fcd20d7).
✅ All tests successful. No failed tests found.

Additional details and impacted files

Files with missing lines	Coverage Δ
src/chain/store/index.rs	85.38% <ø> (ø)

... and 6 files with indirect coverage changes

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