[None][fix] Release stale-range holder after _commit_block in KVCache…#14478
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Tabrizian wants to merge 2 commits into
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[None][fix] Release stale-range holder after _commit_block in KVCache…#14478Tabrizian wants to merge 2 commits into
Tabrizian wants to merge 2 commits into
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…ManagerV2
When _commit_block finalizes a block that is already inside stale_range[lc]
for some finite-window lifecycle (e.g. DSv4 DSA / SWA), the freshly assigned
holder (_PageHolder or _SharedPageLock from line 1268 / 1312-1325) was left
in place. _check_sanity then asserted on the precondition of suspend():
/workspaces/tensorrt_llm/.../sampler.../suspend()
-> _kv_cache.py:931 assert self._check_sanity()
-> _kv_cache.py:1531 assert holder is None # for committed stale block
This trips deterministically on DSv4-Pro disagg GEN runs under MAX_UTILIZATION
scheduling: when the V2 scheduler tries to suspend an in-flight request to
make room, the precondition check aborts the worker. The previously-known
release paths (_on_stop_committing, _unlock_stale_blocks) never revisit a
committed-and-already-stale ordinal, so a 'commit-into-stale-range' case
slipped through.
Fix: at the tail of _commit_block, for the committed block, iterate each
non-SSM lifecycle and clear beam_block[lc] when the ordinal lies inside
that lifecycle's stale_range. The committed page itself remains alive in
the radix tree (committed pages are shareable across caches); only this
_KVCache's redundant strong reference is dropped, restoring the
'committed AND stale -> holder is None' invariant.
Validated end-to-end on DSv4-Pro disagg sweep on Lyris GB300 (c=4/8/16/32/64,
DEP8/TEP8): zero _check_sanity AssertionError across ~160k commit-into-stale
events under real traffic.
Signed-off-by: Iman Tabrizian <10105175+tabrizian@users.noreply.github.com>
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…ManagerV2
When _commit_block finalizes a block that is already inside stale_range[lc] for some finite-window lifecycle (e.g. DSv4 DSA / SWA), the freshly assigned holder (_PageHolder or _SharedPageLock from line 1268 / 1312-1325) was left in place. _check_sanity then asserted on the precondition of suspend():
/workspaces/tensorrt_llm/.../sampler.../suspend()
-> _kv_cache.py:931 assert self._check_sanity()
-> _kv_cache.py:1531 assert holder is None # for committed stale block
This trips deterministically on DSv4-Pro disagg GEN runs under MAX_UTILIZATION scheduling: when the V2 scheduler tries to suspend an in-flight request to make room, the precondition check aborts the worker. The previously-known release paths (_on_stop_committing, _unlock_stale_blocks) never revisit a committed-and-already-stale ordinal, so a 'commit-into-stale-range' case slipped through.
Fix: at the tail of _commit_block, for the committed block, iterate each non-SSM lifecycle and clear beam_block[lc] when the ordinal lies inside that lifecycle's stale_range. The committed page itself remains alive in the radix tree (committed pages are shareable across caches); only this _KVCache's redundant strong reference is dropped, restoring the 'committed AND stale -> holder is None' invariant.
Validated end-to-end on DSv4-Pro disagg sweep on Lyris GB300 (c=4/8/16/32/64, DEP8/TEP8): zero _check_sanity AssertionError across ~160k commit-into-stale events under real traffic.
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