change cuda env to npu

Signed-off-by: wangli <wangli858794774@gmail.com>

Author: Potabk

vllm_ascend/device_allocator/camem.py

@@ -17,6 +17,7 @@
 # CANN-mem-based pytorch pluggable allocator to implement sleep mode.
 #
 import dataclasses
+import os
 from contextlib import contextmanager
 from typing import Any, Callable, Dict, Optional, Tuple, Union
 
@@ -143,6 +144,12 @@ def get_instance() -> "CaMemAllocator":
         return CaMemAllocator.instance
 
     def __init__(self):
+        conf = os.environ.get("PYTORCH_NPU_ALLOC_CONF", "")
+        assert "expandable_segments:True" not in conf, \
+            ("Expandable segments are not compatible with memory pool. "
+            "Please track https://github.com/pytorch/pytorch/issues/147851 "
+            "for the latest updates.")
+
         self.pointer_to_data: Dict[int, AllocationData] = {}
         self.current_tag: str = CaMemAllocator.default_tag
         self.allocator_and_pools: Dict[str, Any] = {}