[refactor] refactor memory constants usage (#31865)

Signed-off-by: Andy Xie <andy.xning@gmail.com>

vllm/config/cache.py

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+import math
 from dataclasses import field
 from typing import TYPE_CHECKING, Any, Literal
 
@@ -10,7 +11,7 @@ from pydantic.dataclasses import dataclass
 from vllm.config.utils import config
 from vllm.logger import init_logger
 from vllm.utils.mem_constants import GiB_bytes
-from vllm.utils.mem_utils import get_cpu_memory
+from vllm.utils.mem_utils import format_gib, get_cpu_memory
 
 if TYPE_CHECKING:
     from vllm.config.parallel import ParallelConfig
@@ -214,7 +215,7 @@ class CacheConfig:
         self,
         parallel_config: ParallelConfig,
     ) -> None:
-        swap_space_bytes = self.swap_space * GiB_bytes
+        swap_space_bytes = math.ceil(self.swap_space * GiB_bytes)
         total_cpu_memory = get_cpu_memory()
         # FIXME(woosuk): Here, it is assumed that the GPUs in a tensor parallel
         # group are in the same node. However, the GPUs may span multiple nodes.
@@ -222,8 +223,8 @@ class CacheConfig:
         cpu_memory_usage = swap_space_bytes * num_gpus_per_node
 
         msg = (
-            f"{cpu_memory_usage / GiB_bytes:.2f} GiB out of the "
-            f"{total_cpu_memory / GiB_bytes:.2f} GiB total CPU memory "
+            f"{format_gib(cpu_memory_usage)} GiB out of the "
+            f"{format_gib(total_cpu_memory)} GiB total CPU memory "
             "is allocated for the swap space."
         )
         if cpu_memory_usage > 0.7 * total_cpu_memory: