enable DCP#1641
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Resolve conflicts between "[feat][DCP] Enable MLA DCP" and current main. Principle: preserve all of main's functionality; layer DCP behavior additively, gated on dcp_world_size > 1 so the default (dcp=1) path is byte-for-byte main. Conflicts resolved: - config.py / arg_utils.py: keep both DCP (-dcp) and main's PCP (-pcp) parallel config + engine args; DCP post-init assert + prefix-cache disable. - block_manager.py: keep main's can_allocate/allocate cache-hit logic, inject DCP _dcp_num_blocks()/_effective_block_size() for local block counts. - model_runner.py: pass both prefill_context_model_parallel_size and decode_context_parallel_size to aiter init_dist_env. - attention_mla.py: DCP RoPE workaround + interleaved slot_mapping + combine (all_gather LSE + cp_lse_ag_out_rs) alongside main's seg/shuffle MLA; DCP num_kv_splits = max(1, 16 // dcp_world_size). Move orphaned DCP init block (dcp_group/_cp_triton_ctx) out of dead code into __init__. - attentions/backends.py: DCP interleaved virtual_block_size slot_mapping branch alongside main's first/last-block path. - plugin/vllm/attention/layer_mla.py (renamed from plugin/attention_mla.py): main already carried DCP scaffolding but _forward_decode returned lse=None, breaking its own decode combine. Make _forward_decode return the real lse when dcp>1 (return_lse), disable persistent mode under DCP, and keep the decode slot_mapping<0 concat_and_cache workaround (adapted to main's self._k_scale / attn_metadata.slot_mapping accessors). Verified: black + ruff clean on resolved files; all 720 tests collect; relevant unit tests (scheduler, block_manager, arg_utils, quant_config) pass in isolation. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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July 20, 2026 04:46
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