[Performance] Move apply_w8a8_block_fp8_linear to an op class (#24666)

Signed-off-by: ElizaWszola <ewszola@redhat.com>
Signed-off-by: ElizaWszola <elizaw.9289@gmail.com>
Signed-off-by: Luka Govedič <lgovedic@redhat.com>
Signed-off-by: Luka Govedič <ProExpertProg@users.noreply.github.com>
Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>
Co-authored-by: Michael Goin <mgoin64@gmail.com>
Co-authored-by: Luka Govedič <lgovedic@redhat.com>

vllm/config/__init__.py

@@ -687,6 +687,23 @@ class VllmConfig:
                     # local attention.
                     self.scheduler_config.disable_hybrid_kv_cache_manager = True
 
+        def has_blocked_weights():
+            if self.quant_config is not None:
+                if hasattr(self.quant_config, "weight_block_size"):
+                    return self.quant_config.weight_block_size is not None
+                elif hasattr(self.quant_config, "has_blocked_weights"):
+                    return self.quant_config.has_blocked_weights()
+            return False
+
+        # Enable quant_fp8 CUDA ops (TODO disable in follow up)
+        # On H100 the CUDA kernel is faster than
+        # native implementation
+        # https://github.com/vllm-project/vllm/issues/25094
+        if has_blocked_weights():
+            custom_ops = self.compilation_config.custom_ops
+            if "none" not in custom_ops and "-quant_fp8" not in custom_ops:
+                custom_ops.append("+quant_fp8")
+
     def update_sizes_for_sequence_parallelism(self,
                                               possible_sizes: list) -> list:
         # remove the sizes that not multiple of tp_size when