Repository: vllm-project/vllm
Issue category: Feature Request

[Usage]: Is it possible to start 8 tp=1 LLMEngine on a 8-GPU machine?
### Your current environment

```text
Collecting environment information...
/home/corvo/.local/lib/python3.10/site-packages/transformers/utils/hub.py:124: FutureWarning: Using `TRANSFORMERS_CACHE` is deprecated and will be removed in v5 of Transformers. Use `HF_HOME` instead.
  warnings.warn(
PyTorch version: 2.3.0+cu121
Is debug build: False
CUDA used to build PyTorch: 12.1
ROCM used to build PyTorch: N/A

OS: Ubuntu 22.04.4 LTS (x86_64)
GCC version: (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Clang version: Could not collect
CMake version: version 3.28.3
Libc version: glibc-2.35

Python version: 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] (64-bit runtime)
Python platform: Linux-5.10.213-201.855.amzn2.x86_64-x86_64-with-glibc2.35
Is CUDA available: True
CUDA runtime version: 12.4.99
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration:
GPU 0: NVIDIA A100-SXM4-40GB
GPU 1: NVIDIA A100-SXM4-40GB
GPU 2: NVIDIA A100-SXM4-40GB
GPU 3: NVIDIA A100-SXM4-40GB
GPU 4: NVIDIA A100-SXM4-40GB
GPU 5: NVIDIA A100-SXM4-40GB
GPU 6: NVIDIA A100-SXM4-40GB
GPU 7: NVIDIA A100-SXM4-40GB

Nvidia driver version: 535.161.08
cuDNN version: Probably one of the following:
/usr/lib/x86_64-linux-gnu/libcudnn.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_adv.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_cnn.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_precompiled.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_runtime_compiled.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_graph.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_heuristic.so.9.0.0
/usr/lib/x86_64-linux-gnu/libcudnn_ops.so.9.0.0
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Architecture:                       x86_64
CPU op-mode(s):                     32-bit, 64-bit
Address sizes:                      46 bits physical, 48 bits virtual
Byte Order:                         Little Endian
CPU(s):                             96
On-line CPU(s) list:                0-95
Vendor ID:                          GenuineIntel
Model name:                         Intel(R) Xeon(R) Platinum 8275CL CPU @ 3.00GHz
CPU family:                         6
Model:                              85
Thread(s) per core:                 2
Core(s) per socket:                 24
Socket(s):                          2
Stepping:                           7
BogoMIPS:                           5999.99
Flags:                              fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq monitor ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single pti fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves ida arat pku ospke
Hypervisor vendor:                  KVM
Virtualization type:                full
L1d cache:                          1.5 MiB (48 instances)
L1i cache:                          1.5 MiB (48 instances)
L2 cache:                           48 MiB (48 instances)
L3 cache:                           71.5 MiB (2 instances)
NUMA node(s):                       2
NUMA node0 CPU(s):                  0-23,48-71
NUMA node1 CPU(s):                  24-47,72-95
Vulnerability Gather data sampling: Unknown: Dependent on hypervisor status
Vulnerability Itlb multihit:        KVM: Mitigation: VMX unsupported
Vulnerability L1tf:                 Mitigation; PTE Inversion
Vulnerability Mds:                  Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state unknown
Vulnerability Meltdown:             Mitigation; PTI
Vulnerability Mmio stale data:      Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state unknown
Vulnerability Retbleed:             Vulnerable
Vulnerability Spec rstack overflow: Not affected
Vulnerability Spec store bypass:    Vulnerable
Vulnerability Spectre v1:           Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:           Mitigation; Retpolines, STIBP disabled, RSB filling
Vulnerability Srbds:                Not affected
Vulnerability Tsx async abort:      Not affected

Versions of relevant libraries:
[pip3] numpy==1.24.4
[pip3] nvidia-nccl-cu12==2.20.5
[pip3] onnx==1.15.0rc2
[pip3] optree==0.10.0
[pip3] pytorch-quantization==2.1.2
[pip3] pytorch-triton==2.2.0+e28a256d7
[pip3] torch==2.3.0
[pip3] torch-tensorrt==2.3.0a0
[pip3] torchdata==0.7.1a0
[pip3] torchtext==0.17.0a0
[pip3] torchvision==0.18.0a0
[pip3] triton==2.3.0
[pip3] vllm-nccl-cu12==2.18.1.0.4.0
[conda] Could not collectROCM Version: Could not collect
Neuron SDK Version: N/A
vLLM Version: 0.4.2
vLLM Build Flags:
CUDA Archs: 5.2 6.0 6.1 7.0 7.2 7.5 8.0 8.6 8.7 9.0+PTX; ROCm: Disabled; Neuron: Disabled
GPU Topology:
GPU0	GPU1	GPU2	GPU3	GPU4	GPU5	GPU6	GPU7	CPU Affinity	NUMA Affinity	GPU NUMA ID
GPU0	 X 	NV12	NV12	NV12	NV12	NV12	NV12	NV12	0-23,48-71	0		N/A
GPU1	NV12	 X 	NV12	NV12	NV12	NV12	NV12	NV12	0-23,48-71	0		N/A
GPU2	NV12	NV12	 X 	NV12	NV12	NV12	NV12	NV12	0-23,48-71	0		N/A
GPU3	NV12	NV12	NV12	 X 	NV12	NV12	NV12	NV12	0-23,48-71	0		N/A
GPU4	NV12	NV12	NV12	NV12	 X 	NV12	NV12	NV12	24-47,72-95	1		N/A
GPU5	NV12	NV12	NV12	NV12	NV12	 X 	NV12	NV12	24-47,72-95	1		N/A
GPU6	NV12	NV12	NV12	NV12	NV12	NV12	 X 	NV12	24-47,72-95	1		N/A
GPU7	NV12	NV12	NV12	NV12	NV12	NV12	NV12	 X 	24-47,72-95	1		N/A

Legend:

  X    = Self
  SYS  = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI)
  NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node
  PHB  = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU)
  PXB  = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge)
  PIX  = Connection traversing at most a single PCIe bridge
  NV#  = Connection traversing a bonded set of # NVLinks
```


### How would you like to use vllm

Below code will try to init LLM on the 1st GPU, causing GPU OOM.
```
from vllm import LLM

for i in range(8):
    llm = LLM(
        model="/models/mistral-7b",
        tensor_parallel_size=1,
    )
```
[Usage]: How to start vLLM on a particular GPU?
### Your current environment

```
Collecting environment information...
PyTorch version: 2.3.0+cu121
Is debug build: False
CUDA used to build PyTorch: 12.1
ROCM used to build PyTorch: N/A

OS: Ubuntu 20.04.6 LTS (x86_64)
GCC version: (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0 
Clang version: Could not collect
CMake version: version 3.29.3
Libc version: glibc-2.31

Python version: 3.11.9 (main, Apr 19 2024, 16:48:06) [GCC 11.2.0] (64-bit runtime)
Python platform: Linux-5.15.0-1056-azure-x86_64-with-glibc2.31
Is CUDA available: True
CUDA runtime version: 11.8.89
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration:
GPU 0: NVIDIA A100 80GB PCIe
GPU 1: NVIDIA A100 80GB PCIe

Nvidia driver version: 545.23.08
cuDNN version: Probably one of the following:
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_adv_infer.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_adv_train.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_cnn_infer.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_cnn_train.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_ops_infer.so.8.7.0
/usr/local/cuda-11.8/targets/x86_64-linux/lib/libcudnn_ops_train.so.8.7.0
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Architecture:                       x86_64
CPU op-mode(s):                     32-bit, 64-bit 
Byte Order:                         Little Endian  
Address sizes:                      48 bits physical, 48 bits virtual
CPU(s):                             48
On-line CPU(s) list:                0-47
Thread(s) per core:                 1
Core(s) per socket:                 48
Socket(s):                          1
NUMA node(s):                       2
Vendor ID:                          AuthenticAMD   
CPU family:                         25
Model:                              1
Model name:                         AMD EPYC 7V13 64-Core Processor
Stepping:                           1
CPU MHz:                            2445.437
BogoMIPS:                           4890.87
Hypervisor vendor:                  Microsoft
Virtualization type:                full
L1d cache:                          1.5 MiB
L1i cache:                          1.5 MiB
L2 cache:                           24 MiB
L3 cache:                           192 MiB
NUMA node0 CPU(s):                  0-23
NUMA node1 CPU(s):                  24-47
Vulnerability Gather data sampling: Not affected   
Vulnerability Itlb multihit:        Not affected   
Vulnerability L1tf:                 Not affected   
Vulnerability Mds:                  Not affected   
Vulnerability Meltdown:             Not affected   
Vulnerability Mmio stale data:      Not affected   
Vulnerability Retbleed:             Not affected   
Vulnerability Spec rstack overflow: Mitigation; safe RET, no microcode
Vulnerability Spec store bypass:    Vulnerable
Vulnerability Spectre v1:           Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:           Mitigation; Retpolines, STIBP disabled, RSB filling, PBRSB-eIBRS Not affected
Vulnerability Srbds:                Not affected   
Vulnerability Tsx async abort:      Not affected   
Flags:                              fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl tsc_reliable nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm cmp_legacy cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw topoext perfctr_core invpcid_single vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves clzero xsaveerptr rdpru arat umip vaes vpclmulqdq rdpid fsrm

Versions of relevant libraries:
[pip3] numpy==1.26.4
[pip3] nvidia-nccl-cu12==2.20.5
[pip3] torch==2.3.0
[pip3] triton==2.3.0
[pip3] vllm_nccl_cu12==2.18.1.0.4.0
[conda] numpy                     1.26.4                   pypi_0    pypi
[conda] nvidia-nccl-cu12          2.20.5                   pypi_0    pypi
[conda] torch                     2.3.0                    pypi_0    pypi
[conda] triton                    2.3.0                    pypi_0    pypi
[conda] vllm-nccl-cu12            2.18.1.0.4.0             pypi_0    pypiROCM Version: Could not collect
Neuron SDK Version: N/A
vLLM Version: 0.4.2
vLLM Build Flags:
CUDA Archs: Not Set; ROCm: Disabled; Neuron: Disabled
GPU Topology:
GPU0    GPU1    NIC0    CPU Affinity    NUMA Affinity   GPU NUMA ID
GPU0     X      NV12    SYS     0-23    0               N/A
GPU1    NV12     X      SYS     24-47   1               N/A
NIC0    SYS     SYS      X

Legend:

  X    = Self
  SYS  = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI)
  NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node
  PHB  = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU)
  PXB  = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge)
  PIX  = Connection traversing at most a single PCIe bridge
  NV#  = Connection traversing a bonded set of # NVLinks

NIC Legend:

  NIC0: mlx5_0
```


### How would you like to use vllm

I have two GPUs in my VM... I am already using vLLM on one of the GPUs and the other one is vacant.
How can I start a second vLLM instance on the second GPU of mine?

I tried:
```bash
--device cuda    |    --device auto    |    --device cuda:1
```
but they don't seem to work as I was expecting...


Could you please tell me what am I missing here?


Regards!


Functions to edit:
vllm/config.py:ParallelConfig.__init__
vllm/distributed/device_communicators/custom_all_reduce.py:CustomAllreduce.__init__
vllm/distributed/device_communicators/custom_all_reduce_utils.py:gpu_p2p_access_check
vllm/executor/multiproc_gpu_executor.py:MultiprocessingGPUExecutor._init_executor

Patch:
diff --git a/vllm/config.py b/vllm/config.py
index 2513d43ce8e6b..a0bd6b0975a16 100644
--- a/vllm/config.py
+++ b/vllm/config.py
@@ -11,7 +11,8 @@
 from vllm.model_executor.layers.quantization import QUANTIZATION_METHODS
 from vllm.model_executor.models import ModelRegistry
 from vllm.transformers_utils.config import get_config, get_hf_text_config
-from vllm.utils import get_cpu_memory, is_cpu, is_hip, is_neuron, is_tpu
+from vllm.utils import (cuda_device_count_stateless, get_cpu_memory, is_cpu,
+                        is_hip, is_neuron, is_tpu)
 
 if TYPE_CHECKING:
     from ray.util.placement_group import PlacementGroup
@@ -605,12 +606,11 @@ def __init__(
         if self.distributed_executor_backend is None and self.world_size > 1:
             # We use multiprocessing by default if world_size fits on the
             # current node and we aren't in a ray placement group.
-            from torch.cuda import device_count
 
             from vllm.executor import ray_utils
             backend = "mp"
             ray_found = ray_utils.ray is not None
-            if device_count() < self.world_size:
+            if cuda_device_count_stateless() < self.world_size:
                 if not ray_found:
                     raise ValueError("Unable to load Ray which is "
                                      "required for multi-node inference")
diff --git a/vllm/distributed/device_communicators/custom_all_reduce.py b/vllm/distributed/device_communicators/custom_all_reduce.py
index bbc2284f8a364..2f8ffe87d4809 100644
--- a/vllm/distributed/device_communicators/custom_all_reduce.py
+++ b/vllm/distributed/device_communicators/custom_all_reduce.py
@@ -12,6 +12,7 @@
 from vllm.distributed.parallel_state import (
     get_local_rank, get_tensor_model_parallel_cpu_group, is_in_the_same_node)
 from vllm.logger import init_logger
+from vllm.utils import cuda_device_count_stateless
 
 try:
     import pynvml
@@ -149,7 +150,7 @@ def __init__(self,
         if cuda_visible_devices:
             device_ids = list(map(int, cuda_visible_devices.split(",")))
         else:
-            device_ids = list(range(torch.cuda.device_count()))
+            device_ids = list(range(cuda_device_count_stateless()))
 
         physical_device_id = device_ids[device.index]
         tensor = torch.tensor([physical_device_id],
diff --git a/vllm/distributed/device_communicators/custom_all_reduce_utils.py b/vllm/distributed/device_communicators/custom_all_reduce_utils.py
index 4b89a23dfc463..b3d397de72cc1 100644
--- a/vllm/distributed/device_communicators/custom_all_reduce_utils.py
+++ b/vllm/distributed/device_communicators/custom_all_reduce_utils.py
@@ -13,6 +13,7 @@
 import vllm.envs as envs
 from vllm.distributed.parallel_state import get_cpu_world_group, get_local_rank
 from vllm.logger import init_logger
+from vllm.utils import cuda_device_count_stateless
 
 logger = init_logger(__name__)
 
@@ -153,7 +154,7 @@ def gpu_p2p_access_check(i: int, j: int) -> bool:
 
     is_distributed = dist.is_initialized()
 
-    num_dev = torch.cuda.device_count()
+    num_dev = cuda_device_count_stateless()
     cuda_visible_devices = envs.CUDA_VISIBLE_DEVICES
     if cuda_visible_devices is None:
         cuda_visible_devices = ",".join(str(i) for i in range(num_dev))
diff --git a/vllm/executor/multiproc_gpu_executor.py b/vllm/executor/multiproc_gpu_executor.py
index 99c9e52034cc1..8385e56f88b39 100644
--- a/vllm/executor/multiproc_gpu_executor.py
+++ b/vllm/executor/multiproc_gpu_executor.py
@@ -9,7 +9,8 @@
                                                   ResultHandler, WorkerMonitor)
 from vllm.logger import init_logger
 from vllm.sequence import ExecuteModelRequest, SamplerOutput
-from vllm.utils import (get_distributed_init_method, get_ip, get_open_port,
+from vllm.utils import (cuda_device_count_stateless,
+                        get_distributed_init_method, get_ip, get_open_port,
                         get_vllm_instance_id, make_async)
 
 logger = init_logger(__name__)
@@ -33,8 +34,7 @@ def _init_executor(self) -> None:
         # Disable torch async compiling which won't work with daemonic processes
         os.environ["TORCHINDUCTOR_COMPILE_THREADS"] = "1"
 
-        from torch.cuda import device_count
-        assert world_size <= device_count(), (
+        assert world_size <= cuda_device_count_stateless(), (
             "please set tensor_parallel_size to less than max local gpu count")
 
         distributed_init_method = get_distributed_init_method(
diff --git a/vllm/utils.py b/vllm/utils.py
index af585929d1a09..b5c42605ba358 100644
--- a/vllm/utils.py
+++ b/vllm/utils.py
@@ -693,3 +693,38 @@ def inner(*args, **kwargs):
         return inner  # type: ignore
 
     return wrapper
+
+
+@lru_cache(maxsize=8)
+def _cuda_device_count_stateless(
+        cuda_visible_devices: Optional[str] = None) -> int:
+    # Note: cuda_visible_devices is not used, but we keep it as an argument for
+    # LRU Cache purposes.
+
+    # Code below is based on
+    # https://github.com/pytorch/pytorch/blob/
+    # c1cd946818442aca8c7f812b16d187ce1586c3bc/
+    # torch/cuda/__init__.py#L831C1-L831C17
+    import torch.cuda
+    import torch.version
+
+    if not torch.cuda._is_compiled():
+        return 0
+    # bypass _device_count_nvml() if rocm (not supported)
+    nvml_count = -1 if torch.version.hip else torch.cuda._device_count_nvml()
+    r = torch._C._cuda_getDeviceCount() if nvml_count < 0 else nvml_count
+    return r
+
+
+def cuda_device_count_stateless() -> int:
+    """Get number of CUDA devices, caching based on the value of
+    CUDA_VISIBLE_DEVICES at the time of call.
+    
+    This should be used instead of torch.cuda.device_count()
+    unless CUDA_VISIBLE_DEVICES has already been set to the desired
+    value."""
+
+    # This can be removed and simply replaced with torch.cuda.get_device_count
+    # after https://github.com/pytorch/pytorch/pull/122815 is released.
+
+    return _cuda_device_count_stateless(envs.CUDA_VISIBLE_DEVICES)

Test patch: diff --git a/.buildkite/test-pipeline.yaml b/.buildkite/test-pipeline.yaml
index 6b12d19ba611f..6a2932db9f2dc 100644
--- a/.buildkite/test-pipeline.yaml
+++ b/.buildkite/test-pipeline.yaml
@@ -48,6 +48,7 @@ steps:
   - TEST_DIST_MODEL=meta-llama/Llama-2-7b-hf DISTRIBUTED_EXECUTOR_BACKEND=mp pytest -v -s distributed/test_chunked_prefill_distributed.py
   - pytest -v -s spec_decode/e2e/test_integration_dist.py
   - CUDA_VISIBLE_DEVICES=0,1 pytest -v -s test_sharded_state_loader.py
+  - CUDA_VISIBLE_DEVICES=0,1 pytest -v -s distributed/test_utils.py
 
 - label: Distributed Tests (Multiple Groups)
   #mirror_hardwares: [amd]
diff --git a/tests/conftest.py b/tests/conftest.py
index e0680467d78b9..5e482466e1c64 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,8 +1,6 @@
 import contextlib
 import gc
 import os
-import subprocess
-import sys
 from typing import Any, Dict, List, Optional, Tuple, TypeVar
 
 import pytest
@@ -21,7 +19,7 @@
 from vllm.multimodal import MultiModalData
 from vllm.multimodal.image import ImageFeatureData, ImagePixelData
 from vllm.sequence import SampleLogprobs
-from vllm.utils import is_cpu
+from vllm.utils import cuda_device_count_stateless, is_cpu
 
 logger = init_logger(__name__)
 
@@ -537,15 +535,4 @@ def num_gpus_available():
     """Get number of GPUs without initializing the CUDA context
     in current process."""
 
-    try:
-        out = subprocess.run([
-            sys.executable, "-c",
-            "import torch; print(torch.cuda.device_count())"
-        ],
-                             capture_output=True,
-                             check=True,
-                             text=True)
-    except subprocess.CalledProcessError as e:
-        logger.warning("Failed to get number of GPUs.", exc_info=e)
-        return 0
-    return int(out.stdout.strip())
+    return cuda_device_count_stateless()
diff --git a/tests/distributed/test_utils.py b/tests/distributed/test_utils.py
new file mode 100644
index 0000000000000..b7ec59c7a2cc6
--- /dev/null
+++ b/tests/distributed/test_utils.py
@@ -0,0 +1,31 @@
+import os
+
+import ray
+
+from vllm.utils import cuda_device_count_stateless
+
+
+@ray.remote
+class _CUDADeviceCountStatelessTestActor():
+
+    def get_count(self):
+        return cuda_device_count_stateless()
+
+    def set_cuda_visible_devices(self, cuda_visible_devices: str):
+        os.environ["CUDA_VISIBLE_DEVICES"] = cuda_visible_devices
+
+    def get_cuda_visible_devices(self):
+        return os.environ["CUDA_VISIBLE_DEVICES"]
+
+
+def test_cuda_device_count_stateless():
+    """Test that cuda_device_count_stateless changes return value if
+    CUDA_VISIBLE_DEVICES is changed."""
+
+    actor = _CUDADeviceCountStatelessTestActor.options(num_gpus=2).remote()
+    assert ray.get(actor.get_cuda_visible_devices.remote()) == "0,1"
+    assert ray.get(actor.get_count.remote()) == 2
+    ray.get(actor.set_cuda_visible_devices.remote("0"))
+    assert ray.get(actor.get_count.remote()) == 1
+    ray.get(actor.set_cuda_visible_devices.remote(""))
+    assert ray.get(actor.get_count.remote()) == 0