fix: Fix poor generation with FP8 Gemma3 1B checkpoint (#6499)

Signed-off-by: Balaram Buddharaju <169953907+brb-nv@users.noreply.github.com>

tensorrt_llm/_torch/models/modeling_gemma3.py

@@ -158,25 +158,29 @@ class Gemma3Attention(Attention):
 
 class Gemma3MLP(nn.Module):
 
-    def __init__(self, config: Gemma3TextConfig):
+    def __init__(self, model_config: ModelConfig[Gemma3TextConfig]):
         super().__init__()
-        self.config = config
-        self.hidden_size = config.hidden_size
-        self.intermediate_size = config.intermediate_size
-        self.dtype = config.torch_dtype
+        self.config = model_config.pretrained_config
+        self.hidden_size = self.config.hidden_size
+        self.intermediate_size = self.config.intermediate_size
+        self.dtype = self.config.torch_dtype
+        self.quant_config = model_config.get_quant_config()
         self.gate_proj = Linear(self.hidden_size,
                                 self.intermediate_size,
                                 bias=False,
-                                dtype=self.dtype)
+                                dtype=self.dtype,
+                                quant_config=self.quant_config)
         self.up_proj = Linear(self.hidden_size,
                               self.intermediate_size,
                               bias=False,
-                              dtype=self.dtype)
+                              dtype=self.dtype,
+                              quant_config=self.quant_config)
         self.down_proj = Linear(self.intermediate_size,
                                 self.hidden_size,
                                 bias=False,
-                                dtype=self.dtype)
-        self.act_fn = ACT2FN[config.hidden_activation]
+                                dtype=self.dtype,
+                                quant_config=self.quant_config)
+        self.act_fn = ACT2FN[self.config.hidden_activation]
 
     @torch.inference_mode()
     def forward(self, x):
@@ -202,7 +206,7 @@ class Gemma3DecoderLayer(DecoderLayer):
             is_sliding=is_sliding,
         )
 
-        self.mlp = Gemma3MLP(config)
+        self.mlp = Gemma3MLP(model_config=model_config)
 
         self.input_layernorm = RMSNorm(hidden_size=config.hidden_size,
                                        eps=config.rms_norm_eps,

tests/integration/defs/accuracy/references/cnn_dailymail.yaml

@@ -1,5 +1,8 @@
 google/gemma-3-1b-it:
   - accuracy: 22.988
+  - quant_algo: FP8
+    kv_cache_quant_algo: FP8
+    accuracy: 22.988
 google/gemma-3-27b-it:
   - accuracy: 28.90
 gpt2:

tests/integration/defs/accuracy/references/mmlu.yaml

@@ -100,6 +100,11 @@ mistralai/Mistral-Small-3.1-24B-Instruct-2503:
   - accuracy: 81.7
 google/gemma-2-9b-it:
   - accuracy: 73.05
+google/gemma-3-1b-it:
+  - accuracy: 39.0
+  - quant_algo: FP8
+    kv_cache_quant_algo: FP8
+    accuracy: 39.0
 google/gemma-3-27b-it:
   - accuracy: 77.80
 Qwen/Qwen2-0.5B-Instruct:

tests/integration/defs/accuracy/test_llm_api_pytorch.py

@@ -604,6 +604,22 @@ class TestGemma3_1BInstruct(LlmapiAccuracyTestHarness):
             task.evaluate(llm)
             task = GSM8K(self.MODEL_NAME)
             task.evaluate(llm)
+            task = MMLU(self.MODEL_NAME)
+            task.evaluate(llm)
+
+    def test_fp8_prequantized(self):
+        # Disabling kv cache reuse as a WAR to deal with gaps in kernel support for Gemma3's non-inclusive sliding window size.
+        kv_cache_config = KvCacheConfig(enable_block_reuse=False,
+                                        enable_partial_reuse=False,
+                                        dtype="fp8")
+        prequantized_model_path = f"{llm_models_root()}/gemma/gemma-3-1b-it-fp8/"
+        with LLM(prequantized_model_path,
+                 kv_cache_config=kv_cache_config) as llm:
+            assert llm.args.quant_config.quant_algo == QuantAlgo.FP8
+            task = CnnDailymail(self.MODEL_NAME)
+            task.evaluate(llm)
+            task = MMLU(self.MODEL_NAME)
+            task.evaluate(llm)
 
     def test_auto_dtype_vswa(self):
         # NOTE: Test with VSWA kv cache config.

tests/integration/test_lists/test-db/l0_h100.yml

@@ -191,6 +191,7 @@ l0_h100:
   - accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_fp8_block_scales[mtp=eagle-fp8kv=False-attention_dp=False-cuda_graph=False-overlap_scheduler=True-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_fp8_block_scales[mtp=vanilla-fp8kv=False-attention_dp=False-cuda_graph=False-overlap_scheduler=False-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_no_kv_cache_reuse[quant_dtype=none-mtp_nextn=2-fp8kv=False-attention_dp=True-cuda_graph=True-overlap_scheduler=True]
+  - accuracy/test_llm_api_pytorch.py::TestGemma3_1BInstruct::test_fp8_prequantized
   - accuracy/test_llm_api_pytorch.py::TestGemma3_27BInstruct::test_auto_dtype
   - accuracy/test_llm_api_pytorch.py::TestMistralSmall24B::test_auto_dtype
   - accuracy/test_llm_api_pytorch.py::TestQwen3_30B_A3B::test_fp8_block_scales[latency]