tcmalloc: Expose flag and parameter for unbacked hugepage subrelease mode - #943
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…mode Expose the `--tcmalloc_subrelease_unbacked_hugepages` flag and `Parameters::set_subrelease_unbacked_hugepages` API to allow configuring unbacked hugepage subrelease mode at startup and dynamically at runtime. Rather than pushing updates into `HugePageFiller` upon flag changes, `HugePageAwareAllocator` reads the parameter lazily during gardening and page release, updating filler state under `pageheap_lock`. To make runtime mode toggling O(1) without requiring expensive list migrations, `PageTracker` now tracks its filler list membership via `in_released_list_`. This ensures trackers unlinking from filler lists correctly identify their origin list and preserve used-page counter invariants without scanning lists on mode changes. PiperOrigin-RevId: 982530158
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tcmalloc: Expose flag and parameter for unbacked hugepage subrelease mode
Expose the
--tcmalloc_subrelease_unbacked_hugepagesflag andParameters::set_subrelease_unbacked_hugepagesAPI to allow configuringunbacked hugepage subrelease mode at startup and dynamically at runtime.
Rather than pushing updates into
HugePageFillerupon flag changes,HugePageAwareAllocatorreads the parameter lazily during gardening and pagerelease, updating filler state under
pageheap_lock.To make runtime mode toggling O(1) without requiring expensive list migrations,
PageTrackernow tracks its filler list membership viain_released_list_.This ensures trackers unlinking from filler lists correctly identify their
origin list and preserve used-page counter invariants without scanning lists
on mode changes.