Refactor sliding window configuration to Transformers best practice (#21927)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

vllm/engine/arg_utils.py

@@ -39,6 +39,7 @@ from vllm.plugins import load_general_plugins
 from vllm.ray.lazy_utils import is_ray_initialized
 from vllm.reasoning import ReasoningParserManager
 from vllm.test_utils import MODEL_WEIGHTS_S3_BUCKET, MODELS_ON_S3
+from vllm.transformers_utils.config import is_interleaved
 from vllm.transformers_utils.utils import check_gguf_file
 from vllm.utils import (STR_DUAL_CHUNK_FLASH_ATTN_VAL, FlexibleArgumentParser,
                         GiB_bytes, get_ip, is_in_ray_actor)
@@ -1081,6 +1082,13 @@ class EngineArgs:
                 "DualChunkFlashAttention is not supported on V1 engine. "
                 "To run the model in V0 engine, try set 'VLLM_USE_V1=0'")
 
+        sliding_window: Optional[int] = None
+        if not is_interleaved(model_config.hf_text_config):
+            # Only set CacheConfig.sliding_window if the model is all sliding
+            # window. Otherwise CacheConfig.sliding_window will override the
+            # global layers in interleaved sliding window models.
+            sliding_window = model_config.get_sliding_window()
+
         cache_config = CacheConfig(
             block_size=self.block_size,
             gpu_memory_utilization=self.gpu_memory_utilization,
@@ -1088,7 +1096,7 @@ class EngineArgs:
             cache_dtype=self.kv_cache_dtype,
             is_attention_free=model_config.is_attention_free,
             num_gpu_blocks_override=self.num_gpu_blocks_override,
-            sliding_window=model_config.get_sliding_window(),
+            sliding_window=sliding_window,
             enable_prefix_caching=self.enable_prefix_caching,
             prefix_caching_hash_algo=self.prefix_caching_hash_algo,
             cpu_offload_gb=self.cpu_offload_gb,