[Core] Make BlockSpaceManagerV2 the default BlockManager to use. (#8678)

Author: sroy745

vllm/config.py

@@ -970,7 +970,7 @@ def __init__(self,
                  max_num_batched_tokens: Optional[int],
                  max_num_seqs: int,
                  max_model_len: int,
-                 use_v2_block_manager: bool = False,
+                 use_v2_block_manager: bool = True,
                  num_lookahead_slots: int = 0,
                  delay_factor: float = 0.0,
                  enable_chunked_prefill: bool = False,

vllm/engine/arg_utils.py

@@ -107,7 +107,7 @@ class EngineArgs:
     block_size: int = 16
     enable_prefix_caching: bool = False
     disable_sliding_window: bool = False
-    use_v2_block_manager: bool = False
+    use_v2_block_manager: bool = True
     swap_space: float = 4  # GiB
     cpu_offload_gb: float = 0  # GiB
     gpu_memory_utilization: float = 0.90
@@ -369,9 +369,12 @@ def add_cli_args(parser: FlexibleArgumentParser) -> FlexibleArgumentParser:
                             action='store_true',
                             help='Disables sliding window, '
                             'capping to sliding window size')
-        parser.add_argument('--use-v2-block-manager',
-                            action='store_true',
-                            help='Use BlockSpaceMangerV2.')
+        parser.add_argument(
+            '--use-v2-block-manager',
+            default=EngineArgs.use_v2_block_manager,
+            action='store_true',
+            help='Use BlockSpaceMangerV2. By default this is set to True. '
+            'Set to False to use BlockSpaceManagerV1')
         parser.add_argument(
             '--num-lookahead-slots',
             type=int,