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[bugfix][DCP] fix block_size of hash in DCP prefix caching #26296

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[bugfix][DCP] fix block_size of hash in DCP prefix caching #26296

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71f8d20
fix bug
heheda12345 Oct 6, 2025
59a6129
clean up
heheda12345 Oct 6, 2025
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10 changes: 2 additions & 8 deletions vllm/v1/core/sched/scheduler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ def __init__(
vllm_config: VllmConfig,
kv_cache_config: KVCacheConfig,
structured_output_manager: StructuredOutputManager,
block_size: int,
mm_registry: MultiModalRegistry = MULTIMODAL_REGISTRY,
include_finished_set: bool = False,
log_stats: bool = False,
Expand Down Expand Up @@ -101,15 +102,8 @@ def __init__(
num_gpu_blocks = self.cache_config.num_gpu_blocks
assert num_gpu_blocks is not None and num_gpu_blocks > 0

self.block_size = self.cache_config.block_size

self.block_size = block_size
self.dcp_world_size = vllm_config.parallel_config.decode_context_parallel_size
# Note(hc): The scheduler’s block_size must be multiplied
# by dcp_world_size, since block hashes are computed on the
# original full token sequence at a granularity of
# original_block_size × dcp_world_size.
if self.dcp_world_size > 1:
self.block_size *= self.dcp_world_size

# req_id -> Request
self.requests: dict[str, Request] = {}
Expand Down
9 changes: 7 additions & 2 deletions vllm/v1/engine/core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -142,12 +142,18 @@ def __init__(
logger.info("Disabling chunked prefill for model without KVCache")
vllm_config.scheduler_config.chunked_prefill_enabled = False

scheduler_block_size = (
vllm_config.cache_config.block_size
* vllm_config.parallel_config.decode_context_parallel_size
)

self.scheduler: SchedulerInterface = Scheduler(
vllm_config=vllm_config,
kv_cache_config=kv_cache_config,
structured_output_manager=self.structured_output_manager,
include_finished_set=vllm_config.parallel_config.data_parallel_size > 1,
log_stats=self.log_stats,
block_size=scheduler_block_size,
)
self.use_spec_decode = vllm_config.speculative_config is not None
if self.scheduler.connector is not None: # type: ignore
Expand Down Expand Up @@ -177,14 +183,13 @@ def __init__(
self.vllm_config.cache_config.enable_prefix_caching
or self.scheduler.get_kv_connector() is not None
):
block_size = vllm_config.cache_config.block_size
caching_hash_fn = get_hash_fn_by_name(
vllm_config.cache_config.prefix_caching_hash_algo
)
init_none_hash(caching_hash_fn)

self.request_block_hasher = get_request_block_hasher(
block_size, caching_hash_fn
scheduler_block_size, caching_hash_fn
)

self.step_fn = (
Expand Down