CP shared-KV prefill batching can present multiple requests to HiCache write-through in one forward. Keeping host free-room admission per request causes repeated small L2 evictions and defeats the free-room policy, while request metadata and radix attachment still need per-request ownership.\n\nThis change adds a batch prepare path that aggregates required host tokens by CP owner lane, performs one host admission/eviction step for the batch, and then reserves/submits each request independently. SessionAwareCache and the scheduler prefer the batch API when available.\n\nConstraint: Radix nodes, host slots, draft slots, rollback, and ack semantics remain per request.\nRejected: Merge reservations or radix nodes across requests | would complicate rollback and writing_check ack ownership.\nRejected: Add collective synchronization for host admission | local owner-lane logic already provides deterministic capacity accounting.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not reintroduce per-request host free-room eviction in the scheduler path without profiling host-full workloads.\nTested: local py_compile for touched Python files\nTested: remote g0034 docker PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py => 117 passed, 5 warnings\nNot-tested: full ETE bs>1 HiCache run under production traffic
CP shared KV now keeps explicit L1 and host free-room targets so pressure is handled by planned eviction instead of repeated capacity-edge retries. The host allocator gains contiguous-preferred page reservation, L1 owner-lane allocation prefers contiguous physical pages, and CP HiCache metadata preserves pending backup safety for page-granular radix updates. Mooncake transfer stats and allocator microbenchmarks are included to make the remaining transfer bottlenecks measurable rather than inferred.
Constraint: CP shared KV uses decode CP size 1 with all prefill CP ranks participating in transfer, so L1/L2 cache residency must remain page-granular and avoid extra collectives.\nConstraint: Production HiCache can be hundreds of GB, so allocator metadata overhead must be visible before enabling aggressive contiguous allocation broadly.\nRejected: Evict only the exact deficit | this keeps the cache at the cliff and causes repeated evict/allocate pressure.\nRejected: Rely on allocator scans alone for contiguity | remote microbenchmarks show fragmented 220GB-equivalent host metadata can make contiguous-preferred scans multi-ms.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not increase L1/L2 free-room defaults or add new CP collectives without ETE evidence and transfer/allocator measurements.\nTested: python -m py_compile on touched runtime/test/benchmark files.\nTested: PYTHONPATH=. python -m pytest -q test/registered/unit/benchmark/test_cp_hicache_allocator_bench.py => 4 passed, 1 warning.\nTested: Remote g0034 log /mnt/beegfs/cjy/log/sglang_cp_hicache_20260601_233723.log shows active prefill process with L1/L2 free-room args, 702 HTTP 200 chat completions, 6272 prefill batches, and no fatal scheduler traceback in latest scan.\nTested: User-reported L1/L2 cache ETE validation passed on remote run.\nNot-tested: Full local pytest suite; local environment is missing several runtime dependencies.\nNot-tested: CUDA allocator microbenchmark during active production prefill process.\nNot-tested: Mooncake straggler fix; stats show transfer tail latency remains a separate bottleneck.
Chunked prefill was skipping prepared CP HiCache backup entirely while still inserting unfinished valid-tail radix state. That combination caused middle chunks to miss reusable host cache and repeatedly hit stale-tail split fallback paths.\n\nThis keeps CP HiCache page-granular: middle chunks now reserve/write only completed pages, and unfinished radix inserts expose only page-complete prefixes while preserving the request-owned sub-page tail in prefix_indices for later chunks.\n\nConstraint: CP HiCache radix and host residency are managed at page granularity, but chunked prefill can end on a sub-page tail.\nRejected: Continue skipping chunked backup | loses middle-chunk reuse and triggers fallback storms.\nRejected: Insert sub-page chunk tails into CP HiCache | creates stale-tail prune/split conflicts against request-owned KV.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not reintroduce chunked_req backup skip; keep CP HiCache chunked inserts page-complete unless the radix/host cache contract becomes sub-page aware.\nTested: python -m py_compile python/sglang/srt/mem_cache/radix_cache.py python/sglang/srt/mem_cache/hiradix_cache.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py\nTested: g0034 targeted chunked CP HiCache regression tests, 2 passed\nTested: g0034 PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py, 107 passed\nNot-tested: Fresh chunked-prefill ETE traffic run after process restart
Prepared per-layer CP HiCache backups can enqueue their final write ack before the radix node is attached. Chunked prefill exposed this window when a separate catch-up backup made writing_check drain the ack queue and pop an unattached node id.
Keep ready but unattached prepared acks queued until insert either attaches the prepared backup or rollback removes the orphan ack. Also document the reactive host free-room eviction plan separately from this state-machine fix.
Constraint: CP HiCache prepared backup transfer can complete before radix insertion attaches node state
Rejected: Drop unknown ack ids | would orphan a later successful prepared attach and leak write state
Rejected: Chunked-only guard | the invalid assumption is in the generic CP write ack state machine
Confidence: high
Scope-risk: narrow
Directive: Do not drain CP write acks unless every ack id is registered in pending_host_backups or ongoing_write_through
Tested: Remote red-green test_cp_hicache_metadata.py::TestHiRadixCacheCPBackup::test_writing_check_defers_unattached_prepared_ack
Tested: Remote PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/mem_cache/test_cp_hicache_load_back_owner_lanes.py (116 passed)
Tested: python -m py_compile python/sglang/srt/mem_cache/hiradix_cache.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py
Not-tested: Full chunked-prefill ETE replay after this commit
Co-authored-by: OmX <omx@oh-my-codex.dev>
Chunked prefill can revisit a sub-page CP HiCache tail while a per-layer backup is still in flight. The old insert path split the radix node first and only then tried to prune the stale tail, so an unprunable pending backup raised after tree mutation and propagated to the scheduler.
This makes split/prune atomic from the radix-tree perspective: drain completed write acks only on the conflict path, preflight pending/unprunable state before split, and return a deferred insert result when the backup is still in flight. Unfinished requests keep their KV ownership for transfer/release instead of rematching or freeing pages under a stale tree state.
Constraint: CP HiCache backup metadata is node/page owned and cannot be repartitioned while per-layer D2H is pending
Rejected: Split the pending backup node | would require repartitioning in-flight backup metadata and host reservations
Rejected: Delete the stale tail unconditionally | risks freeing device/host pages still owned by pending backup
Confidence: high
Scope-risk: moderate
Directive: Do not move stale-tail prune after split without a preflight; pending backup split conflicts must remain non-mutating
Tested: remote g0034 container py_compile for mem_cache files
Tested: remote g0034 PYTHONPATH=python pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/mem_cache/test_cp_hicache_load_back_owner_lanes.py => 115 passed
Tested: local git diff --check
Not-tested: full chunked prefill ETE after service restart
Co-authored-by: OmX <omx@oh-my-codex.dev>
NSA FP8 CP shared-KV reuse must operate on packed page-slot rows, not bf16 compact rows. The change keeps current-only and partial-current reuse inside the page-aligned materialization contract, fails fast for non-page-aligned CP split inputs, and prevents FP8 FlashMLA-KV prefill from reaching incompatible in-seq CP metadata.
Constraint: NSA FP8 persistent MLA KV rows are packed 656-byte records and CP shared KV cache management is page-granular.\nConstraint: FlashMLA-KV prefill metadata is not CP-local after NSA in-seq splitting.\nRejected: Silently splice bf16 current rows into FP8 materialized cache | corrupts the packed cache layout.\nRejected: Keep FP8 FlashMLA-KV auto prefill under NSA CP | reaches num_splits shape errors after q-row splitting.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not re-enable FP8 FlashMLA-KV prefill for NSA in-seq CP until metadata is rebuilt after CP splitting or made CP-local.\nTested: Local git diff --check and py_compile for touched SGLang files.\nTested: Remote g0034 related unit sweep recorded in docs: test_nsa_cp_utils.py, test_cp_shared_kv_layout.py, test_cp_shared_kv_runtime.py, test_cp_hicache_metadata.py passed.\nNot-tested: Full FP8 ETE startup and performance run after this commit.
Page-aligned CP shared KV can pad out_cache_loc beyond valid current rows, so current reuse now gates MLA composition on the valid extend rows and permits draft partial-current reuse once the TAI sparse-page capability check passes. The TAI current-slot path self-tests sparse pages before use and falls back to the torch reference when the installed kernel is stale.
Eviction success and no-op diagnostics were also moved from INFO to DEBUG so owner-lane and host-admission churn does not flood production logs; true write failures remain WARNING.
Constraint: CP shared KV uses page-aligned physical reservations where valid suffix rows can be shorter than padded out_cache_loc.
Constraint: Production failure/fallback logs must remain visible, but hot successful eviction paths should not emit INFO per victim/rank.
Rejected: Keep draft partial-current reuse disabled | would preserve avoidable full materialization on draft cache-hit suffixes.
Rejected: Trust the TAI current-slot kernel unconditionally | stale kernels can corrupt sparse current-page composition.
Confidence: medium
Scope-risk: moderate
Directive: Do not reintroduce INFO logging in eviction hot paths without rate limiting and runtime evidence.
Tested: local py_compile for touched Python files
Tested: local git diff --check
Tested: remote container py_compile for touched Python files
Tested: remote PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py::TestHiCacheEvictLoggingLevels::test_evict_hot_path_success_logs_are_debug_only test/registered/unit/mem_cache/test_cp_shared_kv_runtime.py -> 82 passed, 5 warnings, 2 subtests passed
Not-tested: full ETE traffic after this commit; draft partial-current accept length still needs user-driven runtime validation
The failing runs showed EAGLE accept length collapsing when draft cache-hit suffixes used the new partial-current splice path. This keeps target partial-current reuse enabled, but returns EAGLE/NextN draft cache-hit suffixes to the previous full-materialize path with an explicit fallback warning until the draft splice path has value-level ETE proof.\n\nThe same change set also tightens the page-granular CP HiCache contract for scheduler-visible hits and makes the prefill-to-decode EAGLE handoff observable without cloning hot-path metadata. Exact non-page CP hits are floored to a page boundary for new scheduling decisions, while internal unfinished-request refresh keeps its exact accounting.\n\nConstraint: CP shared KV and HiCache operate at page granularity; exposing token-precise CP tails to scheduler-visible cache hits can force non-page partial materialization.\nConstraint: EAGLE/NextN draft has only one executable layer, so draft prefetch and draft partial-current splice need a separate correctness contract from target layers.\nRejected: Keep draft partial-current splice enabled | remote logs correlate it with avg accept length around 0.068 and median 0.\nRejected: Clone decode metadata tensors on transfer | slot ownership until process_prebuilt consumes them avoids extra hot-path copies.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not re-enable draft partial-current reuse without metadata/draft-KV value checks and ETE accept-length evidence.\nTested: g0034 container py_compile for touched modules.\nTested: g0034 container PYTHONPATH=python python -m pytest -q test/registered/unit/disaggregation/test_decode_queue_compaction.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/mem_cache/test_cp_shared_kv_runtime.py -> 183 passed, 5 warnings, 2 subtests passed.\nNot-tested: Fresh ETE accept-length run after this exact commit; requires user-driven traffic restart.
CP HiCache owns KV at page granularity, but exact valid-tail extension and backed partial-tail split could leave an old sub-page tail child beside a new suffix that reuses the same physical page. That makes radix residency ambiguous across device, host, and draft mirrors. The insert/match split paths now prune stale floored tails when safe, and defer/fail through the existing pending-split path when the subtree is protected or has in-flight backup state.\n\nThis also keeps a temporary scheduler boundary warning for externally observed zero-output responses so future ETE runs can classify whether zero visible output reaches SGLang's output processor.\n\nConstraint: CP shared KV and HiCache manage physical KV by page, while radix keys retain valid-token lengths.\nRejected: Keep overlapping old tail nodes after page-floor split | leaves two independent cache states for one physical tail page.\nRejected: Force-prune protected or in-flight backup tails | can mutate cache state still used by active transfer or inference.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not remove the stale-tail prune without replacing it with another page-granular ownership rule for CP HiCache radix splits.\nTested: Remote py_compile for hiradix_cache.py and scheduler_output_processor_mixin.py in g0034 container.\nTested: Remote PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py -> 97 passed, 5 warnings.\nNot-tested: Full ETE recovery of EAGLE accept length; latest ETE still shows accept collapse, documented in C55.\nNot-tested: Router/client-side output_len=0 correlation when server-side OUTPUT_ZERO_DEBUG does not fire.
CP shared KV HiCache now treats non-page-aligned valid-tail nodes as page-owned when a later request extends beyond them. The prefix probe, match path, insert path, and prepared backup start now agree on flooring the reusable prefix to the previous physical page boundary, so prepared backup metadata cannot start mid-page or fail to attach at insertion.
Duplicate frees under CP HiCache now go through a page-safe free helper. Insert and unfinished duplicate ranges free only fully unprotected pages; no-insert completion still releases the right tail owned only by the finishing request.
Constraint: CP HiCache allocator frees whole physical pages even when called with token-granular locs.
Rejected: Partial-page sharing/refcounting | too complex for the current page-as-minimum-unit contract.
Rejected: Fix only prepare_write_backup_for_req | match_prefix and insert would still expose exact valid-tail hits and desynchronize prepared backup length.
Confidence: medium
Scope-risk: moderate
Directive: Do not expose non-page-aligned CP valid-tail hits to extending requests unless partial-page ownership is explicitly implemented end-to-end.
Tested: remote g0034 py_compile for touched files
Tested: remote g0034 test_cp_hicache_metadata.py 97 passed
Tested: remote g0034 test_cp_shared_kv_runtime.py 73 passed
Not-tested: test_cp_shared_kv_layout.py aborts during installed sgl_kernel architecture-specific op loading before assertions
Async MLA/index prefetch is a scheduling optimization, not the correctness contract for target current reuse. Tiny cache-hit suffixes can skip async prefetcher creation while target partial-current reuse still composes page-slot prefix materialization with current KV rows synchronously. CP HiCache radix/device accounting now treats retained valid-tail pages as physical page spans so allocator state stays consistent when logical cache keys are shorter than the retained page.
Constraint: CP shared KV ownership and HiCache residency are page-granular while request-visible cache lengths remain valid-token lengths.
Constraint: Async prefetch can hang or regress on large-prefix tiny-extend traffic and must not be required for current reuse.
Rejected: Treat missing prefetcher as fail-fast for target partial-current reuse | disabled useful current reuse and broke tiny-prefix/tiny-suffix traffic.
Rejected: Keep async prefetcher object with synchronous consume mode | conflates prefetch object existence with current-layer correctness and hides fallback semantics.
Confidence: medium
Scope-risk: moderate
Directive: Do not make current-only or target partial-current reuse depend on MLA/index prefetcher creation; prefetcher objects mean async next-layer work exists.
Tested: Remote g0034 container py_compile for touched modules.
Tested: Remote g0034 PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_shared_kv_runtime.py -> 73 passed.
Tested: Remote g0034 PYTHONPATH=python python -m pytest -q test/registered/unit/mem_cache/test_cp_hicache_metadata.py -> 90 passed.
Not-tested: Latest full ETE traffic run with GLM-5.1 CP HiCache after this commit.
Not-tested: CUDA kernel-level performance impact of synchronous no-prefetch partial-current compose.
Backed CP HiCache tail splits were floored during match, but write preparation and radix insertion could still observe the raw sub-page prefix. That could skip one token during pre-forward reservation or call CpHiCacheNodeMetadata.split() with a non-page boundary. The shared helper now floors backed partial-tail prefixes before probe, match, and insert.
Constraint: CP HiCache uses page-granular physical ownership while radix keys may keep valid-tail lengths.
Rejected: Let probe and insert keep token-precise tail prefixes | it reintroduces half-page ownership through a different entry point.
Confidence: high
Scope-risk: moderate
Directive: Any CP radix path that can split or reserve against backed HiCache metadata must use the same page-floor policy.
Tested: Remote red tests first for probe and insert failures in g0034 container.
Tested: Remote py_compile for hiradix_cache.py and test_cp_hicache_metadata.py.
Tested: Remote targeted C7 tests: 4 passed, 3 warnings.
Tested: Remote pytest test_cp_hicache_metadata.py test_cp_hicache_load_back_owner_lanes.py: 94 passed, 5 warnings.
Not-tested: Live ETE traffic with concurrent divergent tail prompts.
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP HiCache ownership is page-granular, so a backed radix node must not be split inside a padded physical tail page. When a shorter hit would require an interior tail-page boundary, matching now floors to the previous page boundary and sacrifices the sub-page cache prefix instead of splitting ownership metadata.
Constraint: Host/device/draft CP HiCache metadata tracks page owners and padded physical spans.
Rejected: Split one padded tail page across two radix nodes | it would require half-page ownership semantics and risks double-counting capacity.
Confidence: high
Scope-risk: moderate
Directive: Keep exact valid-tail hits, but floor partial backed-node splits to page boundaries unless metadata gains explicit sub-page ownership.
Tested: Remote py_compile for hiradix_cache.py and test_cp_hicache_metadata.py in g0034 container.
Tested: Remote pytest targeted backed-tail split tests plus exact valid-tail hit test: 3 passed.
Tested: Remote pytest test_cp_hicache_metadata.py test_cp_hicache_load_back_owner_lanes.py: 92 passed, 5 warnings.
Not-tested: Live ETE traffic under divergent short-prefix prompts.
Co-authored-by: OmX <omx@oh-my-codex.dev>
Load-back owner-lane eviction can need to evict a device-resident node whose radix value is a valid tail shorter than the physical tail page. The eviction planner now pads that value only to the page boundary before deriving owner counts, matching the existing write/load capacity contract without exposing padding to radix or scheduler lengths.
Constraint: CP HiCache capacity remains page-owner based while radix node values remain valid-token based.
Constraint: Avoid collectives; owner-lane capacity must be deterministic from local metadata and logical page ids.
Rejected: Require device-resident victim values to be page-aligned | valid-tail cache nodes are now an intentional supported state.
Rejected: Pad to cp_size pages | this would waste KV and violate the page-boundary-only contract.
Confidence: medium
Scope-risk: narrow
Directive: If split-inside-tail support is added later, preserve page ownership/refcount semantics before sharing one padded physical page across radix nodes.
Tested: local py_compile for hiradix_cache.py and touched CP HiCache tests.
Tested: remote g0034 new C8 exact tests: 3 passed, 3 warnings.
Tested: remote g0034 CP HiCache impacted suites: 146 passed, 5 warnings.
Tested: remote g0034 CP shared KV C1-C5 suite: 122 passed, 5 warnings.
Not-tested: full local pytest, blocked by missing runtime dependencies such as starlette.
Not-tested: CUDA E2E runtime for this commit.
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP HiCache now keeps radix and scheduler-visible lengths as valid tokens while host/device transfers reserve and replay the padded physical page span. Exact valid-tail write, insertion, and match paths no longer fall back to page-flooring; the physical owner-lane contract still uses padded page metadata.
Constraint: Scheduler prefix indices must never include padded tail locs.
Constraint: Host/device transfer and owner-lane admission remain page-based.
Rejected: Pad to cp_size or 2*cp_size pages | wastes KV and recreates short-tail fallback behavior.
Rejected: Expose padded locs through load_cp return | would leak fake tokens into req.prefix_indices.
Confidence: medium
Scope-risk: moderate
Directive: Do not implement split-inside-tail by duplicating page_owners without a page-sharing/refcount design.
Tested: local py_compile for touched CP HiCache/radix/controller files and tests.
Tested: remote g0034 CP HiCache impacted suites: 143 passed, 5 warnings.
Tested: remote g0034 CP shared KV C1-C5 suite: 122 passed, 5 warnings.
Not-tested: full local pytest, blocked by missing runtime dependencies such as orjson/starlette.
Not-tested: CUDA E2E runtime for this commit.
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP shared KV and HiCache now use owner-lane metadata as the
authoritative capacity view for host write admission and GPU load-back
planning. This removes the debug scalar capacity env and keeps CP load-back
from relying on a rank-wide scalar collective when per-owner availability is
already known. The load-back planner also accounts for evicting child leaves
that unlock ancestor device residency, which fixes small lane deficits despite
large aggregate evictable capacity.
The commit also adds gated CPU timing logs for CP shared-KV MLA/index
prefetch and a CUDA microbenchmark for comparing dense all-reduce with
owner-packed all-gather layouts. The timing logs are intentionally behind the
existing MLA prefetch log env and should not be enabled for throughput
measurements.
Constraint: CP shared KV owner lanes require target/draft capacity decisions to preserve page_owners rather than total-token scalars
Constraint: CUDA collective benchmarks must run on target GPU hosts, not locally
Rejected: Keep SGLANG_CP_HICACHE_CAPACITY_DEBUG observer env | owner-lane admission now replaces that scalar debug path
Rejected: Add a silent scalar-allreduce fallback | unexpected owner-lane mismatch should fail fast or log loudly
Confidence: medium
Scope-risk: moderate
Directive: Do not reintroduce CP capacity collectives on the scheduler hot path without proving the owner-lane metadata is insufficient
Directive: Disable SGLANG_CP_SHARED_KV_LOG_MLA_PREFETCH for end-to-end performance runs; it is diagnostic and high-volume
Tested: git diff --check
Tested: python -m py_compile on changed runtime/test/benchmark Python files
Tested: remote pytest -q test/registered/unit/mem_cache/test_cp_hicache_load_back_owner_lanes.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py (81 passed, 5 warnings)
Not-tested: CUDA benchmark benchmark/hicache/bench_cp_shared_kv_prefetch_collective.py
Not-tested: full GLM5 E2E throughput after this commit
CP HiCache write-through under shared KV was still using rank-wide collectives to decide host reservation eviction, and per-layer backup registration could be bypassed before the final forward boundary. This moves backup registration to the final run_batch pre-forward boundary, forwards it through SessionAwareCache, exposes fallback paths as explicit warnings, and introduces deterministic owner-lane capacity planning for CP host reservation.
Constraint: CP shared-KV ranks must keep target and draft host reservations owner-lane consistent without adding hot-path collective synchronization
Constraint: Remote CUDA validation must run in the g0034 container, not locally
Rejected: Keep reserve_slots_max all_reduce as the default admission path | observed reserve collectives reaching double-digit and occasional 100ms+ latency
Rejected: Silent post-forward catch-up backup | hides when per-layer forward-overlap backup is not actually active
Confidence: medium
Scope-risk: broad
Directive: Do not reintroduce CP HiCache hot-path collectives without a measured mismatch case and explicit fallback warning
Tested: py_compile for modified Python modules and CP HiCache metadata test file in remote g0034 container
Tested: python3 -m pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py -q in remote g0034 container (75 passed, 5 warnings)
Tested: git diff --check HEAD~1..HEAD
Not-tested: Local pytest blocked by missing pybase64 in the local environment
Not-tested: Full CP HiCache + MTP E2E after the no-collective reservation change
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP shared KV with HiCache and EAGLE needs host backup to overlap forward while keeping radix visibility synchronous. The change reserves host slots before forward, drives target and draft backup from explicit layer-end hooks, and commits host visibility only after the final target/draft ack. It also probes the final insertion prefix before early reservation so repeated EAGLE prompts do not prepare duplicate suffix backups that later rollback as insert_miss.
Constraint: CP ranks use independent shared-KV pools, so target/draft host state must remain atomically visible at the radix boundary.
Constraint: Fused MLA and NSA store paths can bypass store-side notifier hooks, so layer end is the safer backup progress boundary.
Rejected: Store-side backup notifier as the primary trigger | fused store and zero-local paths made notifier coverage fragile.
Rejected: Reserve from cache_protected_len alone | EAGLE bigram/page alignment can make final insertion find a longer existing prefix and force duplicate rollback work.
Confidence: medium
Scope-risk: moderate
Directive: Do not add per-layer CP collectives here; keep radix state synchronous and data transfer asynchronous/local-event driven.
Tested: local git diff --check
Tested: local py_compile for touched CP HiCache/cache-controller/deepseek/test files
Tested: remote pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/managers/test_hicache_controller_cp.py -q (115 passed, 5 warnings)
Not-tested: full GLM5 ETE server rerun after this commit
CP shared KV needs HiCache backup to overlap with layer execution without exposing partially copied host state. Split CP backup into reservation, pending radix state, per-layer target/draft D2H submission, and one final ack-driven visibility commit. The all-layer path remains available only as an explicit fallback and now logs a warning when used.
Constraint: CP shared KV owner-lane metadata and draft/MTP KV must stay strongly synchronized with target KV.
Constraint: Local CUDA tests are disallowed; CUDA verification was run only in the g0034 container.
Rejected: Let target layer hooks copy draft KV too | draft may not have stored that layer yet, which can corrupt MTP accept behavior.
Rejected: Silent all-layer fallback | it hides performance regressions and makes ETE logs ambiguous.
Confidence: medium
Scope-risk: broad
Directive: Reserved or partially copied host payloads must remain invisible until final ack commits pending_host_backups.
Tested: g0034 docker /sgl-workspace/sglang-tai PYTHONPATH=/mnt/beegfs/cjy/tai-kernel/python:python python -m pytest test/registered/unit/managers/test_hicache_controller_cp.py -q -> 49 passed.
Tested: g0034 docker /sgl-workspace/sglang-tai PYTHONPATH=/mnt/beegfs/cjy/tai-kernel/python:python python -m pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py -q -> 58 passed.
Tested: g0034 docker /mnt/beegfs/cjy/tai-kernel PYTHONPATH=python python -m pytest tests/nsa_prefill/test_kvcacheio_lf_pf.py -q -> 7 passed.
Not-tested: Long-running GLM5 CP+HiCache+MTP ETE throughput and host-pressure soak.
CP HiCache now treats draft KV as a strict target-owned payload through pending write visibility, host eviction, and state-buffer registration. Host metadata created before async D2H ack is no longer request-visible, so match_prefix cannot select an in-flight host node. Draft host eviction now fails before target cleanup when draft metadata is missing, and prefill/decode share one helper for draft NSA state buffers so shared-KV mode cannot silently skip mismatched draft state.
Constraint: CP shared KV + HiCache + EAGLE/MTP must not expose target-only host hits or skipped draft state as valid cache hits
Rejected: Rely on event-loop ordering and lock_ref to hide in-flight writes | match_prefix does not consult lock_ref and can observe host_len/cp_hicache directly
Rejected: Keep draft state mismatch as debug-only skip | it can poison speculative acceptance while looking like a successful cache hit
Confidence: high
Scope-risk: moderate
Directive: Do not reintroduce silent draft/target fallback in CP shared-KV HiCache paths; malformed strong-sync metadata should fail fast
Tested: python -m py_compile targeted modified files
Tested: remote g0034 container pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/managers/test_hicache_controller_cp.py test/registered/unit/disaggregation/test_cp_shared_kv_transfer_mapping.py -q (91 passed)
Not-tested: Full CP shared KV + HiCache + EAGLE/MTP ETE server run after this commit
CP HiCache host hits must not advertise target residency unless the draft payload is also valid when EAGLE/MTP draft HiCache is attached. This closes target-only metadata paths by making the CP host-valid predicate and load replay fail fast, resets draft host storage with the target host pool, and records the P1-P3 strong-sync plan state.
The page-index validator is restored for CPU/fake-test tensors only, preserving unit-test coverage for malformed page spans without reintroducing CUDA hot-path host sync.
Constraint: CP shared KV + HiCache + EAGLE/MTP cannot safely demote malformed target/draft metadata to an ordinary cache miss
Rejected: keep permissive fallback for missing draft_host_indices | it can look like a successful cache hit while poisoning speculative acceptance
Rejected: re-enable generic CUDA tensor page validation | it can force host sync in the HiCache transfer hot path
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Do not add silent fallback around CP draft HiCache metadata; unexpected target/draft divergence should fail fast with node/rank context
Tested: remote container targeted tests: 5 passed
Tested: remote container files test_cp_hicache_metadata.py and test_hicache_controller_cp.py: 77 passed
Tested: remote container test_page_index_utils.py: 8 passed
Tested: local git diff --check and py_compile for modified Python files
Not-tested: full CP shared KV + HiCache + EAGLE/MTP ETE
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP HiCache previously let the target host pool and the draft/MTP host pool each consume the full --hicache-size budget. With EAGLE/MTP enabled this doubled per-rank host allocation and could kill scheduler ranks during startup before Python emitted a traceback. The cache now treats target KV and draft KV as one logical host-cache object: target and draft capacities are computed from one per-rank byte budget, draft may receive more token capacity when its per-token footprint is smaller, and draft attachment remains tied to target residency.
Constraint: --hicache-size is a per-rank host budget and must not be multiplied by attaching draft KV.
Rejected: Give draft another independent --hicache-size allocation | repeats the observed host OOM failure mode.
Rejected: Disable draft HiCache attachment under CP | avoids OOM but breaks target/draft cache-hit consistency for MTP.
Confidence: medium
Scope-risk: moderate
Directive: Keep target and draft KV as one logical HiCache object; do not let draft host allocation consume an independent full hicache-size budget.
Tested: python -m py_compile on modified scheduler/cache/test files
Tested: remote g0034 container PYTHONPATH=python python -m pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py -q (45 passed)
Not-tested: full multi-rank GLM5 server restart after clearing existing remote router/defunct process state
Co-authored-by: OmX <omx@oh-my-codex.dev>
HiCache host hits can be skipped before load-back when the quota gate only counts immediately free KV allocator space. Under CP shared-KV pressure most reusable capacity may be represented as evictable radix-cache leaves, so the gate can incorrectly reject a host hit and leave prefill with cached-token zero despite host residency. Count device evictable cache in the quota estimate while leaving actual owner-lane allocation and eviction checks in the load path.
Constraint: CP HiCache load-back still has to respect owner-lane allocation and allocator eviction semantics.
Rejected: Force load-back regardless of quota | would bypass the scheduler pressure signal and increase OOM risk.
Rejected: Treat cache-hit zero as a transfer issue | logs showed host hits were found but skipped by quota before transfer.
Confidence: medium
Scope-risk: moderate
Directive: Do not remove evictable cache from load-back capacity accounting without checking CP HiCache host-hit behavior under device pressure.
Tested: git diff --check
Tested: remote g0034 container pytest -q test/registered/unit/managers/test_prefill_adder.py test/registered/unit/managers/test_hicache_controller_cp.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/mem_cache/test_alloc_pages_with_owners.py (90 passed, 3 warnings)
Not-tested: Full ETE GLM5 CP+HiCache+EAGLE pressure run after this quota change
Co-authored-by: OmX <omx@oh-my-codex.dev>
In CP=8 + NSA-shared-KV + HiCache disagg-prefill, cache-hit prefill produced
incoherent decode output. Cold prefill on CP was correct; pure CP without
HiCache was correct. The bug lived at the HiCache load_cp / device-alloc
interface.
Root cause: cache_controller.load_cp called the plain
mem_pool_device_allocator.alloc(logical_len), which returns logical pages
with no CP owner-pattern preservation. Cold prefill instead uses
alloc_extend_compute_owner with a zigzag owner pattern from
build_in_seq_page_compute_owners. The saved CpHiCacheNodeMetadata.owned_positions
records WHICH POSITIONS in the write-time alloc were owned by this rank. At
load time, those same positions are applied to a new alloc whose per-position
owner pattern is arbitrary -- each rank loads its host bytes into physical
slots whose corresponding logical page is owned by a DIFFERENT rank.
Attention's materialize_shared_token_kv_buffer reads from the owner's
physical slot, which was never loaded. Result: garbage.
Fix:
- CpHiCacheNodeMetadata gains two required fields: page_owners (int8 per
logical page, identical on all CP ranks) and page_size. __post_init__
validates; split() bisects page_owners by page index with a page-alignment
check.
- _write_cp derives page_owners from device_indices (page-first slot of each
page -> logical page id -> layout.owner_for_logical_pages) and stores in
both metadata-construction sites (zero-owned and normal).
- New CPSharedPagedTokenToKVPoolAllocator.alloc_pages_with_owners() reuses
_select_compute_owner_pages (with its tai-kernel fast path) and returns
page-contiguous token locs whose per-page owner sequence equals the input.
- load_cp now concats page_owners across nodes_to_load and calls
alloc_pages_with_owners. On None (lane exhausted) the caller hits the
retry-with-eviction path; further failure returns None and degrades to
cache miss. No silent fallback to plain alloc -- that recreated the bug.
- load_back retry path now calls _evict_for_compute_owner_lanes (module-top
import) instead of plain evict(); this targets the deficit lane and gives
the next alloc attempt a chance to satisfy it.
- envs import moved to module top in cache_controller.py per code-review
feedback. Removed an over-defensive owned_check.all().item() in load_cp
that would have re-introduced the host-sync anti-pattern 97a9f850c
removed -- the invariant is already guaranteed by alloc_pages_with_owners.
Tests: 40 existing CpHiCacheNodeMetadata constructions migrated to pass the
new required fields. 9 new metadata tests (validators + split page-alignment).
10 new allocator tests in test_alloc_pages_with_owners.py covering input-order
preservation, lane exhaustion, release_pages fallback, debug-mode invariant.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Cache-hit prefill can skip draft forward for the prefix while PD transfer still reads draft KV for that same prefix. CP HiCache therefore needs to persist draft/MTP KV alongside target KV instead of relying on whatever remains in the draft GPU pool.
Constraint: CP HiCache is host-only here; storage backends remain unsupported for CP shared KV.
Constraint: CP shared KV must keep owner-page semantics and avoid falling back to full KV on every rank.
Rejected: Recompute cached-prefix draft KV during prefill | loses the HiCache benefit and reintroduces the large hidden/KV footprint.
Rejected: Change PD transfer to skip draft prefix KV | decode still needs draft cache continuity for MTP acceptance.
Confidence: medium
Scope-risk: moderate
Directive: Keep target and draft CP HiCache metadata/load/write/evict paths in lockstep; changing one without the other can silently reduce MTP accept length.
Tested: Remote g0034 container /sgl-workspace/sglang-tai: python3 -m pytest -q test/registered/unit/managers/test_hicache_controller_cp.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py => 58 passed, 3 warnings
Not-tested: Full multi-node HiCache+MTP serving benchmark and accept-length recovery.
Cache-hit prefill can skip draft forward for the prefix while PD transfer still reads draft KV for that same prefix. CP HiCache therefore needs to persist draft/MTP KV alongside target KV instead of relying on whatever remains in the draft GPU pool.
Constraint: CP HiCache is host-only here; storage backends remain unsupported for CP shared KV.
Constraint: CP shared KV must keep owner-page semantics and avoid falling back to full KV on every rank.
Rejected: Recompute cached-prefix draft KV during prefill | loses the HiCache benefit and reintroduces the large hidden/KV footprint.
Rejected: Change PD transfer to skip draft prefix KV | decode still needs draft cache continuity for MTP acceptance.
Confidence: medium
Scope-risk: moderate
Directive: Keep target and draft CP HiCache metadata/load/write/evict paths in lockstep; changing one without the other can silently reduce MTP accept length.
Tested: Remote g0034 container /sgl-workspace/sglang-tai: python3 -m pytest -q test/registered/unit/managers/test_hicache_controller_cp.py test/registered/unit/mem_cache/test_cp_hicache_metadata.py => 58 passed, 3 warnings
Not-tested: Full multi-node HiCache+MTP serving benchmark and accept-length recovery.
laoyao0822
leaveletandClaude Opus 4.7
ThomasX