[Quantization] Allow GGUF quantization to skip unquantized layer (#23188)

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>

vllm/model_executor/layers/quantization/gguf.py

@@ -13,7 +13,8 @@ from vllm.logger import init_logger
 from vllm.model_executor.layers.fused_moe.layer import (FusedMoE,
                                                         FusedMoEConfig,
                                                         FusedMoEMethodBase)
-from vllm.model_executor.layers.linear import LinearBase, LinearMethodBase
+from vllm.model_executor.layers.linear import (LinearBase, LinearMethodBase,
+                                               UnquantizedLinearMethod)
 from vllm.model_executor.layers.quantization import QuantizationMethods
 from vllm.model_executor.layers.quantization.base_config import (
     QuantizationConfig, QuantizeMethodBase)
@@ -28,8 +29,10 @@ logger = init_logger(__name__)
 class GGUFConfig(QuantizationConfig):
     """Config class for GGUF."""
 
-    def __init__(self, ) -> None:
+    def __init__(self,
+                 unquantized_modules: Optional[list[str]] = None) -> None:
         super().__init__()
+        self.unquantized_modules = unquantized_modules or []
 
     def __repr__(self) -> str:
         return ("GGUFConfig()")
@@ -55,6 +58,8 @@ class GGUFConfig(QuantizationConfig):
     def get_quant_method(self, layer: torch.nn.Module,
                          prefix: str) -> Optional["QuantizeMethodBase"]:
         if isinstance(layer, LinearBase):
+            if is_layer_skipped_gguf(prefix, self.unquantized_modules):
+                return UnquantizedLinearMethod()
             return GGUFLinearMethod(self)
         elif isinstance(layer, VocabParallelEmbedding):
             return GGUFEmbeddingMethod(self)
@@ -63,6 +68,10 @@ class GGUFConfig(QuantizationConfig):
         return None
 
 
+def is_layer_skipped_gguf(prefix: str, unquantized_modules: list[str]):
+    return any(module_name in prefix for module_name in unquantized_modules)
+
+
 UNQUANTIZED_TYPES = {WeightType.F32, WeightType.F16, WeightType.BF16}
 STANDARD_QUANT_TYPES = {
     WeightType.Q4_0,