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[Bugfix] Fix kvpool precision synchronization #4574

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Merged
merged 2 commits into from
Nov 30, 2025
+1 −6
Merged

[Bugfix] Fix kvpool precision synchronization #4574

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524d7b0
solve precision synchronization
LCAIZJ Nov 29, 2025
04b7188
delete synchronize
LCAIZJ Nov 29, 2025
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4 changes: 0 additions & 4 deletions vllm_ascend/distributed/kvpool/kv_transfer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,6 @@ def _handle_request(self, req_meta: dict[str, Any]):
addr_list.append(addr)
size_list.append(size)
if self.dcp_size > 1:
torch.npu.current_stream().synchronize()
self.m_store.put(key_list, addr_list, size_list)
else:
key_list_tp = key_list[self.tp_rank % self.put_step::self.put_step]
Expand All @@ -126,7 +125,6 @@ def _handle_request(self, req_meta: dict[str, Any]):
size_list_tp = size_list[self.tp_rank %
self.put_step::self.put_step]
if key_list_tp:
torch.npu.current_stream().synchronize()
self.m_store.put(key_list_tp, addr_list_tp, size_list_tp)
if is_last_chunk:
self.set_finished_request(req_id)
Expand Down Expand Up @@ -205,7 +203,6 @@ def _handle_request( # type: ignore[override]
addr_list.append(addr)
size_list.append(size)
if self.dcp_size > 1:
torch.npu.current_stream().synchronize()
self.m_store.put(key_list, addr_list, size_list)
else:
key_list_tp = key_list[self.tp_rank % self.put_step::self.put_step]
Expand All @@ -214,7 +211,6 @@ def _handle_request( # type: ignore[override]
size_list_tp = size_list[self.tp_rank %
self.put_step::self.put_step]
if key_list_tp:
torch.npu.current_stream().synchronize()
self.m_store.put(key_list_tp, addr_list_tp, size_list_tp)
if req_meta.layer_id == self.final_layer_id and req_meta.is_last_chunk:
self.set_finished_request(req_meta.req_id)
Expand Down
3 changes: 1 addition & 2 deletions vllm_ascend/worker/model_runner_v1.py
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Expand Up @@ -2339,7 +2339,6 @@ def execute_model(
attn_metadata, self.with_prefill, maybe_padded_num_tokens,
input_ids, positions, intermediate_tensors, inputs_embeds)

self.maybe_wait_for_kv_save()
finished_sending, finished_recving = self.get_finished_kv_transfer(
scheduler_output)

Expand Down Expand Up @@ -2603,7 +2602,7 @@ def propose_draft_token_ids(sampled_token_ids):
# ngram and other speculative decoding methods use the sampled
# tokens on the CPU, so they are run after bookkeeping.
propose_draft_token_ids(valid_sampled_token_ids)

self.maybe_wait_for_kv_save()
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@gemini-code-assist gemini-code-assist bot Nov 29, 2025

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critical

Moving self.maybe_wait_for_kv_save() to this location from execute_model is a critical fix for a race condition. Previously, the KV cache save operation could be triggered before the model's forward pass had completed, potentially leading to corrupted data being saved. By placing it here, after sampling operations that implicitly synchronize the device, we ensure the KV cache is fully populated and stable before initiating the save.

A minor suggestion for future improvement: the method name maybe_wait_for_kv_save is misleading as it appears to trigger an asynchronous save rather than waiting. Renaming it to something like trigger_kv_save_if_needed would improve code clarity.

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@Pz1116 Pz1116 Nov 29, 2025

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LGTM

if has_kv_transfer_group():
get_kv_transfer_group().clear_connector_metadata()

Expand Down
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