[Bugfix] Avoid repeatedly creating dummy data during engine startup (vllm-project#17935)

DarkLight1337 · mawong-amd · commit 115dec1572ec · 2025-05-13T21:07:23.000Z
Signed-off-by: DarkLight1337 &lt;tlleungac@connect.ust.hk&gt;
diff --git a/vllm/engine/async_llm_engine.py b/vllm/engine/async_llm_engine.py
@@ -1232,6 +1232,9 @@ async def start_profile(self) -> None:
     async def stop_profile(self) -> None:
         self.engine.stop_profile()
 
+    async def reset_mm_cache(self) -> None:
+        self.engine.reset_mm_cache()
+
     async def reset_prefix_cache(self,
                                  device: Optional[Device] = None) -> None:
         self.engine.reset_prefix_cache(device)
diff --git a/vllm/engine/llm_engine.py b/vllm/engine/llm_engine.py
@@ -409,6 +409,9 @@ def get_tokenizer_for_seq(sequence: Sequence) -> AnyTokenizer:
         # the next step without re-scheduling.
         self._skip_scheduling_next_step = False
 
+        # Don't keep the dummy data in memory
+        self.reset_mm_cache()
+
     def _initialize_kv_caches(self) -> None:
         """Initialize the KV cache in the worker(s).
 
@@ -913,6 +916,10 @@ def has_unfinished_requests_for_virtual_engine(
         """
         return self.scheduler[virtual_engine].has_unfinished_seqs()
 
+    def reset_mm_cache(self) -> bool:
+        """Reset the multi-modal cache."""
+        return self.input_preprocessor.mm_registry.reset_processor_cache()
+
     def reset_prefix_cache(self, device: Optional[Device] = None) -> bool:
         """Reset prefix cache for all devices."""
 
diff --git a/vllm/engine/multiprocessing/__init__.py b/vllm/engine/multiprocessing/__init__.py
@@ -123,6 +123,10 @@ class RPCUProfileRequest(Enum):
     STOP_PROFILE = 2
 
 
+class RPCResetMultiModalCacheRequest(Enum):
+    RESET = 1
+
+
 @dataclass
 class RPCResetPrefixCacheRequest:
     device: Device
@@ -164,6 +168,7 @@ class RPCAdapterLoadedResponse:
 
 RPC_REQUEST_T = Union[RPCProcessRequest, RPCAbortRequest, RPCStartupRequest,
                       RPCUProfileRequest, RPCLoadAdapterRequest,
+                      RPCResetMultiModalCacheRequest,
                       RPCResetPrefixCacheRequest, RPCSleepRequest,
                       RPCWakeUpRequest, RPCIsSleepingRequest]
 
diff --git a/vllm/engine/multiprocessing/client.py b/vllm/engine/multiprocessing/client.py
@@ -31,6 +31,7 @@
                                          RPCIsSleepingResponse,
                                          RPCLoadAdapterRequest,
                                          RPCProcessRequest,
+                                         RPCResetMultiModalCacheRequest,
                                          RPCResetPrefixCacheRequest,
                                          RPCSleepRequest, RPCStartupRequest,
                                          RPCStartupResponse,
@@ -687,6 +688,13 @@ async def stop_profile(self) -> None:
         await self._send_one_way_rpc_request(
             request=RPCUProfileRequest.STOP_PROFILE, socket=self.input_socket)
 
+    async def reset_mm_cache(self) -> None:
+        """Reset the multi-modal cache"""
+
+        await self._send_one_way_rpc_request(
+            request=RPCResetMultiModalCacheRequest.RESET,
+            socket=self.input_socket)
+
     async def reset_prefix_cache(self,
                                  device: Optional[Device] = None) -> None:
         """Reset the prefix cache"""
diff --git a/vllm/engine/multiprocessing/engine.py b/vllm/engine/multiprocessing/engine.py
@@ -22,6 +22,7 @@
                                          RPCIsSleepingResponse,
                                          RPCLoadAdapterRequest,
                                          RPCProcessRequest,
+                                         RPCResetMultiModalCacheRequest,
                                          RPCResetPrefixCacheRequest,
                                          RPCSleepRequest, RPCStartupRequest,
                                          RPCStartupResponse,
@@ -269,6 +270,8 @@ def handle_new_input(self):
                         self.stop_profile()
                 elif isinstance(request, RPCLoadAdapterRequest):
                     self._handle_load_adapter_request(request)
+                elif isinstance(request, RPCResetMultiModalCacheRequest):
+                    self.reset_mm_cache()
                 elif isinstance(request, RPCResetPrefixCacheRequest):
                     self.reset_prefix_cache()
                 elif isinstance(request, RPCSleepRequest):
@@ -409,6 +412,9 @@ def start_profile(self) -> None:
     def stop_profile(self) -> None:
         self.engine.stop_profile()
 
+    def reset_mm_cache(self) -> bool:
+        return self.engine.reset_mm_cache()
+
     def reset_prefix_cache(self) -> bool:
         return self.engine.reset_prefix_cache()
 
diff --git a/vllm/engine/protocol.py b/vllm/engine/protocol.py
@@ -278,6 +278,11 @@ async def stop_profile(self) -> None:
         """Start profiling the engine"""
         ...
 
+    @abstractmethod
+    async def reset_mm_cache(self) -> None:
+        """Reset the multi-modal cache"""
+        ...
+
     @abstractmethod
     async def reset_prefix_cache(self,
                                  device: Optional[Device] = None) -> None:
diff --git a/vllm/entrypoints/openai/api_server.py b/vllm/entrypoints/openai/api_server.py
@@ -150,6 +150,10 @@ async def build_async_engine_client(
 
     async with build_async_engine_client_from_engine_args(
             engine_args, args.disable_frontend_multiprocessing) as engine:
+
+        # Don't keep the dummy data in memory
+        await engine.reset_mm_cache()
+
         yield engine
 
 
diff --git a/vllm/multimodal/processing.py b/vllm/multimodal/processing.py
@@ -1026,6 +1026,11 @@ def put(
     def put_item(self, item: ProcessingCacheItem) -> None:
         self._cache[item.key] = item.value
 
+    def reset(self) -> bool:
+        self._cache.clear()
+
+        return True
+
 
 class BaseProcessingInfo:
     """Base class to provide the information necessary for data processing."""
diff --git a/vllm/multimodal/registry.py b/vllm/multimodal/registry.py
@@ -88,6 +88,12 @@ def __init__(self) -> None:
 
         self._processing_cache = ProcessingCache(VLLM_MM_INPUT_CACHE_GIB)
 
+    def reset_processor_cache(self) -> bool:
+        """Reset the multi-modal processing cache."""
+        self._processing_cache.reset()
+
+        return True  # Success
+
     @deprecated("Legacy input processor/mapper pipeline has been removed. "
                 "Please update your model runner to use "
                 "`seq_group_metadata.multi_modal_data` directly without "
@@ -106,7 +112,7 @@ def get_max_tokens_per_item_by_modality(
         if not model_config.is_multimodal_model:
             return {}
 
-        processor = self.create_processor(model_config, disable_cache=True)
+        processor = self.create_processor(model_config, disable_cache=False)
         profiler = MultiModalProfiler(processor)
 
         seq_len = model_config.max_model_len
@@ -190,7 +196,7 @@ def get_mm_limits_per_prompt(
         if not model_config.is_multimodal_model:
             return {}
 
-        processor = self.create_processor(model_config, disable_cache=True)
+        processor = self.create_processor(model_config, disable_cache=False)
         profiler = MultiModalProfiler(processor)
         return profiler.get_mm_limits()
 
@@ -286,7 +292,7 @@ def get_decoder_dummy_data(
 
         The model is identified by ``model_config``.
         """
-        processor = self.create_processor(model_config, disable_cache=True)
+        processor = self.create_processor(model_config, disable_cache=False)
         profiler = MultiModalProfiler(processor)
         dummy_data = profiler.get_decoder_dummy_data(seq_len, mm_counts)
 
@@ -310,7 +316,7 @@ def get_encoder_dummy_data(
 
         The model is identified by ``model_config``.
         """
-        processor = self.create_processor(model_config, disable_cache=True)
+        processor = self.create_processor(model_config, disable_cache=False)
         profiler = MultiModalProfiler(processor)
         dummy_data = profiler.get_encoder_dummy_data(seq_len, mm_counts)
 
diff --git a/vllm/v1/engine/async_llm.py b/vllm/v1/engine/async_llm.py
@@ -476,6 +476,11 @@ async def start_profile(self) -> None:
     async def stop_profile(self) -> None:
         await self.engine_core.profile_async(False)
 
+    async def reset_mm_cache(self) -> None:
+        self.processor.mm_registry.reset_processor_cache()
+        self.processor.mm_input_cache_client.reset()
+        await self.engine_core.reset_mm_cache_async()
+
     async def reset_prefix_cache(self,
                                  device: Optional[Device] = None) -> None:
         if device == Device.CPU:
diff --git a/vllm/v1/engine/core.py b/vllm/v1/engine/core.py
@@ -286,6 +286,15 @@ def shutdown(self):
     def profile(self, is_start: bool = True):
         self.model_executor.profile(is_start)
 
+    def reset_mm_cache(self):
+        # NOTE: Since this is mainly for debugging, we don't attempt to
+        # re-sync the internal caches (P0 processor, P0 mirror, P1 mirror)
+        if self.scheduler.get_num_unfinished_requests():
+            logger.warning("Resetting the multi-modal cache when requests are "
+                           "in progress may lead to desynced internal caches.")
+
+        self.mm_input_cache_server.reset()
+
     def reset_prefix_cache(self):
         self.scheduler.reset_prefix_cache()
 
diff --git a/vllm/v1/engine/core_client.py b/vllm/v1/engine/core_client.py
@@ -88,6 +88,9 @@ def add_request(self, request: EngineCoreRequest) -> None:
     def profile(self, is_start: bool = True) -> None:
         raise NotImplementedError
 
+    def reset_mm_cache(self) -> None:
+        raise NotImplementedError
+
     def reset_prefix_cache(self) -> None:
         raise NotImplementedError
 
@@ -143,6 +146,9 @@ async def add_request_async(self, request: EngineCoreRequest) -> None:
     async def profile_async(self, is_start: bool = True) -> None:
         raise NotImplementedError
 
+    async def reset_mm_cache_async(self) -> None:
+        raise NotImplementedError
+
     async def reset_prefix_cache_async(self) -> None:
         raise NotImplementedError
 
@@ -214,6 +220,9 @@ def shutdown(self) -> None:
     def profile(self, is_start: bool = True) -> None:
         self.engine_core.profile(is_start)
 
+    def reset_mm_cache(self) -> None:
+        self.engine_core.reset_mm_cache()
+
     def reset_prefix_cache(self) -> None:
         self.engine_core.reset_prefix_cache()
 
@@ -600,6 +609,9 @@ def abort_requests(self, request_ids: list[str]) -> None:
     def profile(self, is_start: bool = True) -> None:
         self.call_utility("profile", is_start)
 
+    def reset_mm_cache(self) -> None:
+        self.call_utility("reset_mm_cache")
+
     def reset_prefix_cache(self) -> None:
         self.call_utility("reset_prefix_cache")
 
@@ -787,6 +799,9 @@ async def abort_requests_async(self, request_ids: list[str]) -> None:
     async def profile_async(self, is_start: bool = True) -> None:
         await self.call_utility_async("profile", is_start)
 
+    async def reset_mm_cache_async(self) -> None:
+        await self.call_utility_async("reset_mm_cache")
+
     async def reset_prefix_cache_async(self) -> None:
         await self.call_utility_async("reset_prefix_cache")
 
diff --git a/vllm/v1/engine/llm_engine.py b/vllm/v1/engine/llm_engine.py
@@ -101,6 +101,9 @@ def __init__(
             # for v0 compatibility
             self.model_executor = self.engine_core.engine_core.model_executor  # type: ignore
 
+        # Don't keep the dummy data in memory
+        self.reset_mm_cache()
+
     @classmethod
     def from_vllm_config(
         cls,
@@ -240,6 +243,11 @@ def start_profile(self):
     def stop_profile(self):
         self.engine_core.profile(False)
 
+    def reset_mm_cache(self):
+        self.processor.mm_registry.reset_processor_cache()
+        self.processor.mm_input_cache_client.reset()
+        self.engine_core.reset_mm_cache()
+
     def reset_prefix_cache(self, device: Optional[Device] = None):
         self.engine_core.reset_prefix_cache()
 
diff --git a/vllm/v1/engine/mm_input_cache.py b/vllm/v1/engine/mm_input_cache.py
@@ -83,3 +83,8 @@ def get_and_update_p1(
             full_mm_inputs.append(mm_input)
 
         return full_mm_inputs
+
+    def reset(self) -> bool:
+        self.mm_cache.clear()
+
+        return True
diff --git a/vllm/v1/engine/processor.py b/vllm/v1/engine/processor.py
@@ -54,6 +54,10 @@ def __init__(
         self.use_hash = self.mm_input_cache_client.use_cache or \
             self.cache_config.enable_prefix_caching
 
+    @property
+    def mm_registry(self):
+        return self.input_preprocessor.mm_registry
+
     def _validate_logprobs(
         self,
         params: SamplingParams,
