perf: batch allocate overflow pages in BTreeMap#357
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Pull Request Overview
This PR improves the performance of writing large keys/values into a BTreeMap by preallocating overflow pages, which helps avoid repeated page allocations. Key changes include:
- Renaming and using a unified variable (position) in both read and write loops for clarity.
- Adding a preallocation step for overflow pages in the NodeWriter.
- Updating benchmark result YAMLs to reflect performance improvements.
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| src/btreemap/node/io.rs | Refactored read/write loops and added batch allocation of overflow pages. |
| benchmarks/vec/canbench_results.yml | Updated benchmark metrics for vec operations. |
| benchmarks/compare/canbench_results.yml | Updated benchmark metrics for compare operations. |
| benchmarks/btreeset/canbench_results.yml | Updated benchmark metrics for btreeset operations. |
| benchmarks/btreemap/canbench_results.yml | Updated benchmark metrics for btreemap operations. |
Comments suppressed due to low confidence (2)
src/btreemap/node/io.rs:243
- Consider adding a clarifying comment about how 'end_offset' is determined and how compute_num_overflow_pages_needed handles edge cases, to help future maintainers understand the overflow preallocation logic.
compute_num_overflow_pages_needed(end_offset, self.page_size.get() as u64) as usize;
src/btreemap/node/io.rs:266
- [nitpick] Verify that the transition from using 'bytes_written' to 'position' consistently preserves the intended semantics when processing segments of varying lengths.
match page_idx {
maksymar
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mraszyk
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Jul 1, 2025
mraszyk
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Jul 1, 2025
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This PR improves performance of writing big keys/values into BTreeMap that take several pages.
Now it preallocate overflow pages in advance, which helps in cases of allocating a single chunk of bytes, say 10 MB.
Improvement on
write_chunks_btreemap_1benchmark is -1.37% instructions.