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[doc] Fold long code blocks to improve readability (#19926)

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Signed-off-by: reidliu41 <reid201711@gmail.com>
Co-authored-by: reidliu41 <reid201711@gmail.com>
This commit is contained in:
Reid
2025-06-23 13:24:23 +08:00
committed by GitHub
parent 493c275352
commit f17aec0d63
50 changed files with 3455 additions and 3180 deletions
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docs/usage/troubleshooting.md
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@@ -60,68 +60,70 @@ To identify the particular CUDA operation that causes the error, you can add `--
If GPU/CPU communication cannot be established, you can use the following Python script and follow the instructions below to confirm whether the GPU/CPU communication is working correctly.
```python
# Test PyTorch NCCL
import torch
import torch.distributed as dist
dist.init_process_group(backend="nccl")
local_rank = dist.get_rank() % torch.cuda.device_count()
torch.cuda.set_device(local_rank)
data = torch.FloatTensor([1,] * 128).to("cuda")
dist.all_reduce(data, op=dist.ReduceOp.SUM)
torch.cuda.synchronize()
value = data.mean().item()
world_size = dist.get_world_size()
assert value == world_size, f"Expected {world_size}, got {value}"
??? Code
print("PyTorch NCCL is successful!")
```python
# Test PyTorch NCCL
import torch
import torch.distributed as dist
dist.init_process_group(backend="nccl")
local_rank = dist.get_rank() % torch.cuda.device_count()
torch.cuda.set_device(local_rank)
data = torch.FloatTensor([1,] * 128).to("cuda")
dist.all_reduce(data, op=dist.ReduceOp.SUM)
torch.cuda.synchronize()
value = data.mean().item()
world_size = dist.get_world_size()
assert value == world_size, f"Expected {world_size}, got {value}"
# Test PyTorch GLOO
gloo_group = dist.new_group(ranks=list(range(world_size)), backend="gloo")
cpu_data = torch.FloatTensor([1,] * 128)
dist.all_reduce(cpu_data, op=dist.ReduceOp.SUM, group=gloo_group)
value = cpu_data.mean().item()
assert value == world_size, f"Expected {world_size}, got {value}"
print("PyTorch NCCL is successful!")
print("PyTorch GLOO is successful!")
# Test PyTorch GLOO
gloo_group = dist.new_group(ranks=list(range(world_size)), backend="gloo")
cpu_data = torch.FloatTensor([1,] * 128)
dist.all_reduce(cpu_data, op=dist.ReduceOp.SUM, group=gloo_group)
value = cpu_data.mean().item()
assert value == world_size, f"Expected {world_size}, got {value}"
if world_size <= 1:
exit()
print("PyTorch GLOO is successful!")
# Test vLLM NCCL, with cuda graph
from vllm.distributed.device_communicators.pynccl import PyNcclCommunicator
if world_size <= 1:
exit()
pynccl = PyNcclCommunicator(group=gloo_group, device=local_rank)
# pynccl is enabled by default for 0.6.5+,
# but for 0.6.4 and below, we need to enable it manually.
# keep the code for backward compatibility when because people
# prefer to read the latest documentation.
pynccl.disabled = False
# Test vLLM NCCL, with cuda graph
from vllm.distributed.device_communicators.pynccl import PyNcclCommunicator
pynccl = PyNcclCommunicator(group=gloo_group, device=local_rank)
# pynccl is enabled by default for 0.6.5+,
# but for 0.6.4 and below, we need to enable it manually.
# keep the code for backward compatibility when because people
# prefer to read the latest documentation.
pynccl.disabled = False
s = torch.cuda.Stream()
with torch.cuda.stream(s):
data.fill_(1)
out = pynccl.all_reduce(data, stream=s)
value = out.mean().item()
assert value == world_size, f"Expected {world_size}, got {value}"
print("vLLM NCCL is successful!")
g = torch.cuda.CUDAGraph()
with torch.cuda.graph(cuda_graph=g, stream=s):
out = pynccl.all_reduce(data, stream=torch.cuda.current_stream())
s = torch.cuda.Stream()
with torch.cuda.stream(s):
data.fill_(1)
out = pynccl.all_reduce(data, stream=s)
g.replay()
torch.cuda.current_stream().synchronize()
value = out.mean().item()
assert value == world_size, f"Expected {world_size}, got {value}"
print("vLLM NCCL is successful!")
print("vLLM NCCL with cuda graph is successful!")
g = torch.cuda.CUDAGraph()
with torch.cuda.graph(cuda_graph=g, stream=s):
out = pynccl.all_reduce(data, stream=torch.cuda.current_stream())
data.fill_(1)
g.replay()
torch.cuda.current_stream().synchronize()
value = out.mean().item()
assert value == world_size, f"Expected {world_size}, got {value}"
print("vLLM NCCL with cuda graph is successful!")
dist.destroy_process_group(gloo_group)
dist.destroy_process_group()
```
dist.destroy_process_group(gloo_group)
dist.destroy_process_group()
```
If you are testing with a single node, adjust `--nproc-per-node` to the number of GPUs you want to use:
@@ -165,25 +167,27 @@ WARNING 12-11 14:50:37 multiproc_worker_utils.py:281] CUDA was previously
or an error from Python that looks like this:
```console
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
??? Logs
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
```console
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
if __name__ == '__main__':
freeze_support()
...
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
if __name__ == '__main__':
freeze_support()
...
To fix this issue, refer to the "Safe importing of main module"
section in https://docs.python.org/3/library/multiprocessing.html
```
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
To fix this issue, refer to the "Safe importing of main module"
section in https://docs.python.org/3/library/multiprocessing.html
```
then you must update your Python code to guard usage of `vllm` behind a `if
__name__ == '__main__':` block. For example, instead of this:
@@ -207,20 +211,22 @@ if __name__ == '__main__':
vLLM heavily depends on `torch.compile` to optimize the model for better performance, which introduces the dependency on the `torch.compile` functionality and the `triton` library. By default, we use `torch.compile` to [optimize some functions](https://github.com/vllm-project/vllm/pull/10406) in the model. Before running vLLM, you can check if `torch.compile` is working as expected by running the following script:
```python
import torch
??? Code
@torch.compile
def f(x):
# a simple function to test torch.compile
x = x + 1
x = x * 2
x = x.sin()
return x
```python
import torch
x = torch.randn(4, 4).cuda()
print(f(x))
```
@torch.compile
def f(x):
# a simple function to test torch.compile
x = x + 1
x = x * 2
x = x.sin()
return x
x = torch.randn(4, 4).cuda()
print(f(x))
```
If it raises errors from `torch/_inductor` directory, usually it means you have a custom `triton` library that is not compatible with the version of PyTorch you are using. See [this issue](https://github.com/vllm-project/vllm/issues/12219) for example.