disk_striped: optimize futures vectors #2429
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In the `disk_striped` IO paths, use `Iterator::collect` instead of `push`ing into a `Vec`. Reimplement the chunk iterator to ensure it implements `TrustedLen`. This should ensure there's exactly one allocation for the futures array per IO and that the compiler constructs the futures directly into the array.
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Pull Request Overview
This PR optimizes the performance of futures vector creation in disk_striped I/O functions by using Iterator::collect with iterators that implement TrustedLen, enabling single-allocation vector construction.
Key changes:
- Replaced custom
ChunkIterstruct with inlineRange::mapiterator forTrustedLenoptimization - Simplified error handling by replacing verbose
IoErrorenum with simplerLowerErrorstruct - Refactored futures creation from
forloops withVec::pushto iterator chains with.collect() - Improved test assertions using idiomatic
.expect()and.expect_err()methods
mebersol
previously approved these changes
Dec 1, 2025
gurasinghMS
approved these changes
Dec 10, 2025
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Performance traces show that growing and populating the vector of futures in
disk_stripedIO functions is expensive. Optimize this: useIterator::collectto collect directly into theJoinAllthat we'll await, using an iterator that implementsTrustedLenso that the vector can allocate its buffer once and construct the futures in place.Also, clean up some impossible failure paths.