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Defer segment source requests until cache misses - #96
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phillipleblanc wants to merge 1 commit into
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Create the source request only after a cache miss so warm cache hits and unpolled requests do not enqueue speculative reads. Signed-off-by: Phillip LeBlanc <879445+phillipleblanc@users.noreply.github.com>
lukekim
approved these changes
Sep 17, 2026
This was referenced Sep 17, 2026
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WHAT
Consult the segment cache before creating a source request, so hits and unpolled requests do not register a delegate read. This is a draft experiment with no demonstrated lookup performance benefit; the proposed warm-cache OS-open elimination criterion failed.
WHY
An eager delegate can register work before a cache hit makes it unnecessary.
HOW
Keep miss population and cache-error fallback unchanged; add four regression tests (three fail before the change). All 307 layout/file nextest tests, pinned-toolchain scoped Clippy and formatting pass; built Spice with this exact fork and verified real fixture counts/results, full scans, 64-client profiles and 3,000/s offered profiles.
Paired CPU ms/lookup before → after: no-index 8.068 → 8.332; indexed 4.552 → 4.531; indexed arrival 3.784 → 3.773. Warm read calls and OS-open samples persist. Do not merge for the predicted performance gain.
Detailed local evidence includes exact source/build digests, commands, raw profiles, capture gates and limits; artifacts are retained locally, not uploaded. Runtime validation depends on spiceai/spiceai#14149 and instrumentation spiceai/spiceai#14174; this fork diff has no runtime dependency or machine-local dependency pin. No lab signoff was run, as explicitly instructed.