Add enable_flashinfer_mxfp4_bf16_moe for higher precision and slower moe backend (#9004)

python/sglang/srt/layers/quantization/mxfp4.py

@@ -30,6 +30,7 @@ from sglang.srt.layers.quantization.base_config import (
 )
 from sglang.srt.layers.quantization.utils import is_layer_skipped
 from sglang.srt.layers.utils import is_sm100_supported
+from sglang.srt.managers.schedule_batch import global_server_args_dict
 from sglang.srt.utils import (
     direct_register_custom_op,
     get_bool_env_var,
@@ -262,6 +263,9 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
         self.use_triton_kernels = get_moe_runner_backend().is_triton_kernel()
         self.with_bias = False
         self.use_flashinfer = get_moe_runner_backend().is_flashinfer_mxfp4()
+        self.flashinfer_mxfp4_moe_precision = global_server_args_dict[
+            "flashinfer_mxfp4_moe_precision"
+        ]
 
         self.triton_kernel_moe_forward = None
         self.triton_kernel_moe_with_bias_forward = None
@@ -615,11 +619,29 @@ class Mxfp4MoEMethod(FusedMoEMethodBase):
         from sglang.srt.layers.moe.topk import TopKOutputChecker
 
         if self.use_flashinfer:
-            # Based on profiling results, we need to quantize x to mxfp8 here to achieve better performance
-            x_quant, x_scale = mxfp8_quantize(
-                x, False, alignment=self.hidden_size
-            )  # to mxfp8
-            x_scale = x_scale.view(torch.float8_e4m3fn).reshape(-1)
+            # When bf16 mode is enabled, we don't need to quantize the input,
+            # TRT-LLM automatically handles quantization in the kernel implementation and pipelines it with GEMM operations,
+            # which can theoretically improve performance
+            if self.flashinfer_mxfp4_moe_precision == "bf16":
+                assert x.dtype == torch.bfloat16
+                x_quant = x
+                x_scale = None
+
+                # May be fused later if this code branch is frequently needed
+                origin_hidden_states_dim = x_quant.shape[-1]
+                if self.hidden_size != origin_hidden_states_dim:
+                    x_quant = torch.nn.functional.pad(
+                        x_quant,
+                        (0, self.hidden_size - origin_hidden_states_dim),
+                        mode="constant",
+                        value=0.0,
+                    )
+            elif self.flashinfer_mxfp4_moe_precision == "default":
+                x_quant, x_scale = mxfp8_quantize(x, False, alignment=self.hidden_size)
+                x_scale = x_scale.view(torch.float8_e4m3fn).reshape(-1)
+            else:
+                raise NotImplementedError
+
             assert x_quant.shape[-1] == self.hidden_size
             assert TopKOutputChecker.format_is_bypassed(topk_output)
 

python/sglang/srt/managers/schedule_batch.py

@@ -87,6 +87,7 @@ GLOBAL_SERVER_ARGS_KEYS = [
     "disable_flashinfer_cutlass_moe_fp4_allgather",
     "disable_radix_cache",
     "enable_dp_lm_head",
+    "flashinfer_mxfp4_moe_precision",
     "enable_flashinfer_allreduce_fusion",
     "moe_dense_tp_size",
     "ep_dispatch_algorithm",

python/sglang/srt/server_args.py

@@ -190,6 +190,7 @@ class ServerArgs:
         "flashinfer_cutlass",
         "flashinfer_mxfp4",
     ] = "auto"
+    flashinfer_mxfp4_moe_precision: Literal["default", "bf16"] = "default"
     enable_flashinfer_allreduce_fusion: bool = False
     deepep_mode: Literal["auto", "normal", "low_latency"] = "auto"
     ep_num_redundant_experts: int = 0
@@ -1496,10 +1497,18 @@ class ServerArgs:
                 "triton_kernel",
                 "flashinfer_trtllm",
                 "flashinfer_cutlass",
+                "flashinfer_mxfp4",
             ],
             default=ServerArgs.moe_runner_backend,
             help="Choose the runner backend for MoE.",
         )
+        parser.add_argument(
+            "--flashinfer-mxfp4-moe-precision",
+            type=str,
+            choices=["mxfp4", "bf16"],
+            default=ServerArgs.flashinfer_mxfp4_moe_precision,
+            help="Choose the computation precision of flashinfer mxfp4 moe",
+        )
         parser.add_argument(
             "--enable-flashinfer-allreduce-fusion",
             action="store_true",