On restart the LMDB index + disk-slab blobs persist, but CpL3Store.from_config built the slot
pools all-free and the GC LRU empty -> the next spill re-hands-out a slot the durable index still
references (clobbers a live blob) and GC never reclaims the carried-over entries. Neither a clean
start nor a durable reload was actually realized.
connect() now applies a cold-start policy BEFORE the bg threads start (the write thread is the sole
pool/GC owner, so the single-threaded reconcile must precede it):
- clear (default): wipe the persisted index + reset the pools/GC -> genuinely empty start (disk
blobs are inert, overwritten lazily on slot reuse).
- load: rebuild this rank's slot free-list + GC LRU from the durable disk blobs. Drive the scan
from the rank's OWN slab file (header-only reads) so it never inspects another rank's slots even
when ranks share a disk; a slot is LIVE iff its blob header parses AND the shared index still maps
that content hash back to this exact slot -> occupy + seed the GC LRU with the durable last_access;
orphan/unwritten slots stay free. Header-only (no payload CRC); reload-time verify-on-read still
fail-softs a torn payload. The L3 durable floor now survives a process restart.
Primitives: CpL3SlotPool.rebuild_from_allocated (O(num_slots) bulk-occupy) + CpL3DiskSlab.read_header
(one aligned block, not the multi-MB slot). Env SGLANG_CP_L3_COLD_START (default "clear"), read in
_maybe_init_cp_l3 and passed to connect(). Tests: 4 cold-start e2e (load rebuilds the floor + no slot
collision after a fresh spill; GC LRU rebuilt; clear starts empty; unknown mode fails loud) + 2 unit
(rebuild_from_allocated, read_header). 23 L3 store/disk/posix tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Phase 3.0 (L3 disk durable floor) foundational primitives, pure + unit-tested:
- 64B self-describing blob header (magic/version/payload-kind/content-hash/CRC),
verified on every read (verify_blob) -> torn/bit-rot slots become a MISS, not garbage.
- slot_bytes_for_page: header+payload rounded to the 4K O_DIRECT boundary.
- CpL3SlotPool: O(1) free-list over fixed-size per-payload disk page-slots (the L3
analog of CpSharedL2PageAllocator's free list), fail-loud on double-free/OOB, with
reset() for the flush_cache hook. NOT a ring buffer (eviction frees arbitrary slots).
Rank-local (a rank stores only its owned pages; L3 eviction selection rides the shared
LMDB replicated clock). 12/12 unit tests. Design: docs_internal/cp_hicache_l3_phase3_impl_design.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leaveletandClaude Opus 4.8