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[Draft]optimize dp allreduce #2492

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[Draft]optimize dp allreduce #2492

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15b115b
optimize dp allreduce
Angazenn Aug 22, 2025
03d7903
fix lint
Angazenn Aug 22, 2025
d9e687b
comment
Angazenn Aug 25, 2025
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27 changes: 15 additions & 12 deletions vllm_ascend/worker/model_runner_v1.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,6 @@
import numpy.typing as npt
import torch
import torch._dynamo.cache_size
import torch.distributed as dist
import torch.nn as nn
from tqdm import tqdm # type: ignore
from vllm.attention import AttentionType, get_attn_backend
Expand Down Expand Up @@ -587,17 +586,21 @@ def _get_forward_metadata_across_dp(
self, num_tokens: int, with_prefill: bool,
enable_dbo: bool) -> tuple[torch.Tensor, bool, bool]:

# Compose: all_reduce metadata (num_tokens of each rank, with_prefill, enable_dbo)
num_tokens_across_dp = torch.zeros(self.dp_size + 2,
dtype=torch.int32,
device="cpu")
num_tokens_across_dp[self.dp_rank] = num_tokens
num_tokens_across_dp[-2] = int(with_prefill)
num_tokens_across_dp[-1] = int(not enable_dbo)
dist.all_reduce(num_tokens_across_dp, group=get_dp_group().cpu_group)
with_prefill = bool(num_tokens_across_dp[-2])
enable_dbo = not bool(num_tokens_across_dp[-1])
num_tokens_across_dp = num_tokens_across_dp[:-2]
local_forward_metadata = torch.tensor(
[[num_tokens, with_prefill, enable_dbo]],
device="npu",
dtype=torch.int32)
# use device all_gather
global_forward_metadata = get_dp_group().all_gather(
local_forward_metadata, dim=0)
maybe_padded_num_tokens = global_forward_metadata[:, 0].max().item()
num_tokens_across_dp = torch.tensor([maybe_padded_num_tokens] *
self.dp_size,
device="cpu",
dtype=torch.int32)
with_prefill = bool(global_forward_metadata[:, 1].any())
enable_dbo = bool(global_forward_metadata[:, 2].any())

return num_tokens_across_dp, with_prefill, enable_dbo

def _get_forward_metadata_across_dp_and_pad(
Expand Down
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