[KV Connector] Opt DecodeBenchConnector into SupportsHMA
Previously the HMA (hybrid KV cache manager) layer refused to activate
when DecodeBenchConnector was in use, because the connector did not
advertise SupportsHMA. That forced decode-only benchmark recipes to
pass --disable-hybrid-kv-cache-manager, which collapsed hybrid-model
KV cache groups (SWA / MLA compress=4 / MLA compress=128 / sparse
indexer) into a single uniform page size via unify_kv_cache_spec_
page_size, throwing away the compression savings and capping concurrent
capacity on hybrid models (e.g. DeepSeek-V4 saw ~43 concurrent
8k/1k requests instead of the model's true ceiling).
This connector is a dummy fill that owns no external per-block state,
so the HMA path has nothing extra to do. Implementation is minimal:
- Inherit from SupportsHMA.
- Implement request_finished_all_groups: delegates to the same
scheduler.request_finished() cleanup as the single-group variant,
ignoring block_ids (no per-block state to release).
With this change, recipes can drop --disable-hybrid-kv-cache-manager
and let HMA size each KV cache group correctly.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Zijing Liu <liuzijing2014@gmail.com>
