Slice: Add prefetch deduplication and freelist - #12949
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Track in-flight prefetches per remap instance using a mutex- protected set to prevent duplicate upstream requests. Recycle BgBlockFetch objects via a freelist under the same mutex. Fire the initial prefetch burst at header parse time so faster clients benefit sooner. Co-Authored-By: Craig Taylor (and research)
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Pull request overview
This PR enhances the slice plugin’s background prefetching by deduplicating in-flight prefetch requests per remap Config instance and reusing BgBlockFetch objects via a mutex-protected freelist. It also triggers the initial prefetch burst earlier (at server header-parse time) to improve time-to-first-byte for fast clients.
Changes:
- Add
schedule_prefetch()helper and shift initial prefetch scheduling to server response header parse time. - Update
BgBlockFetch::schedule()to accept a URL-derived key and deduplicate viaConfig-owned tracking. - Add
Configprefetch state: mutex + active-key set + freelist, with cleanup inConfigdestructor.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| plugins/slice/util.h | Exposes schedule_prefetch() helper. |
| plugins/slice/util.cc | Implements schedule_prefetch() and uses it for sliding-window prefetching. |
| plugins/slice/server.cc | Schedules initial prefetch burst once response headers are parsed. |
| plugins/slice/prefetch.h | Extends BgBlockFetch with config/key state and updated schedule() signature. |
| plugins/slice/prefetch.cc | Implements dedup + freelist release/cleanup and integrates them into bg fetch lifecycle. |
| plugins/slice/Config.h | Adds prefetch dedup/freelist data structures and APIs. |
| plugins/slice/Config.cc | Implements prefetchAcquire() and calls cleanup from Config destructor (plus UNITTEST stubs). |
Guard prefetchCleanup() with m_prefetch_mutex to prevent data race with concurrent prefetchRelease() calls. Add unit tests for prefetchAcquire() dedup semantics. Add missing #include <string_view> to prefetch.h. Null-guard the result of TSUrlStringGet() in schedule_prefetch() before constructing std::string_view.
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Addressed Co-Pilot's concerns. |
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[approve ci] |
zwoop
marked this pull request as ready for review
April 7, 2026 21:53
traeak
approved these changes
May 26, 2026
traeak
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These changes are fine. They could use an autest to issue multiple in parallel requests but not necessary.
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Cherry-picked to 10.2.x |
cmcfarlen
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Jun 16, 2026
* Slice: Add prefetch deduplication and freelist Track in-flight prefetches per remap instance using a mutex- protected set to prevent duplicate upstream requests. Recycle BgBlockFetch objects via a freelist under the same mutex. Fire the initial prefetch burst at header parse time so faster clients benefit sooner. Co-Authored-By: Craig Taylor (and research) * Address Copilot review comments Guard prefetchCleanup() with m_prefetch_mutex to prevent data race with concurrent prefetchRelease() calls. Add unit tests for prefetchAcquire() dedup semantics. Add missing #include <string_view> to prefetch.h. Null-guard the result of TSUrlStringGet() in schedule_prefetch() before constructing std::string_view. (cherry picked from commit cfae05c)
cmcfarlen
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Jul 29, 2026
* Slice: Add prefetch deduplication and freelist Track in-flight prefetches per remap instance using a mutex- protected set to prevent duplicate upstream requests. Recycle BgBlockFetch objects via a freelist under the same mutex. Fire the initial prefetch burst at header parse time so faster clients benefit sooner. Co-Authored-By: Craig Taylor (and research) * Address Copilot review comments Guard prefetchCleanup() with m_prefetch_mutex to prevent data race with concurrent prefetchRelease() calls. Add unit tests for prefetchAcquire() dedup semantics. Add missing #include <string_view> to prefetch.h. Null-guard the result of TSUrlStringGet() in schedule_prefetch() before constructing std::string_view.
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Track in-flight prefetches per remap instance using a mutex- protected set to prevent duplicate upstream requests. Recycle BgBlockFetch objects via a freelist under the same mutex. Fire the initial prefetch burst at header parse time so faster clients benefit sooner.
Co-Authored-By: Craig Taylor (who also did all the investigations"