[Bugfix] fix v1 cpu worker fails on macOS (#19121)

vllm/engine/arg_utils.py

@@ -1290,7 +1290,7 @@ class EngineArgs:
         # Skip this check if we are running on a non-GPU platform,
         # or if the device capability is not available
         # (e.g. in a Ray actor without GPUs).
-        from vllm.platforms import current_platform
+        from vllm.platforms import CpuArchEnum, current_platform
         if (current_platform.is_cuda()
                 and current_platform.get_device_capability()
                 and current_platform.get_device_capability().major < 8):
@@ -1434,7 +1434,8 @@ class EngineArgs:
         # Non-[CUDA, TPU] may be supported on V1, but off by default for now.
         v0_hardware = not any(
             (current_platform.is_cuda(), current_platform.is_tpu(),
-             current_platform.is_cpu()))
+             (current_platform.is_cpu()
+              and current_platform.get_cpu_architecture() == CpuArchEnum.X86)))
         if v0_hardware and _warn_or_fallback(  # noqa: SIM103
                 current_platform.device_name):
             return False

vllm/platforms/cpu.py

@@ -2,6 +2,7 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 import os
+import platform
 import sys
 from importlib.util import find_spec
 from typing import TYPE_CHECKING, Optional
@@ -22,6 +23,15 @@ else:
     VllmConfig = None
 
 
+def get_max_threads(pid=0):
+    if hasattr(os, 'sched_getaffinity'):
+        return len(os.sched_getaffinity(pid))
+    elif platform.system() == 'Darwin':
+        return os.cpu_count()
+    else:
+        raise NotImplementedError("Unsupported OS")
+
+
 class CpuPlatform(Platform):
     _enum = PlatformEnum.CPU
     device_name: str = "cpu"
@@ -190,7 +200,7 @@ class CpuPlatform(Platform):
 
         # Note: to avoid the error 'nthreads cannot be larger than environment
         #  variable "NUMEXPR_MAX_THREADS" (64)'.
-        os.environ["NUMEXPR_MAX_THREADS"] = str(len(os.sched_getaffinity(0)))
+        os.environ["NUMEXPR_MAX_THREADS"] = str(get_max_threads())
 
         # Set default threads num for OpenMP parallel
         os.environ["OMP_NUM_THREADS"] = str(torch.get_num_threads())