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[Bugfix] Fix custom all reduce nvlink check on multi node #4903

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esmeetu wants to merge 4 commits into from
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[Bugfix] Fix custom all reduce nvlink check on multi node #4903

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dc24273
fix
esmeetu May 19, 2024
d3f396d
apply comments
esmeetu May 19, 2024
6689ec8
fix check
esmeetu May 19, 2024
4a092ba
add sort
esmeetu May 19, 2024
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7 changes: 7 additions & 0 deletions vllm/distributed/device_communicators/custom_all_reduce.py
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,13 @@ def __init__(self,
dist.all_gather(gather_list, tensor, group=self.group)
physical_device_ids = [t.item() for t in gather_list]

# 3 nodes will be like [0,1,2,3,0,1,0,1]
if sorted(physical_device_ids)[-1] + 1 != world_size:
logger.warning(
"Custom allreduce is disabled because this feature is "
"not intended for multi node use case.")
return

Comment on lines +152 to +158
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@youkaichao youkaichao May 19, 2024

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This is still not safe. It is possible, that one node uses gpu 0, 1 , while the other node uses 2, 3, and the world size is 4. In this case, we cannot use custom allreduce. However, this code will not capture it.

# test nvlink first, this will filter out most of the cases
# where custom allreduce is not supported
# this checks hardware and driver support for NVLink
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