Support FP8 MLA prefill and 128k context. (#14395)

python/sglang/srt/layers/attention/trtllm_mla_backend.py

@@ -21,6 +21,7 @@ from sglang.srt.layers.attention.utils import (
     get_num_page_per_block_flashmla,
 )
 from sglang.srt.layers.dp_attention import get_attention_tp_size
+from sglang.srt.layers.quantization.fp8_kernel import scaled_fp8_quant
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch, ForwardMode
 from sglang.srt.server_args import get_global_server_args
 from sglang.srt.utils import is_cuda, is_flashinfer_available, is_float4_e2m1fn_x2
@@ -39,7 +40,7 @@ if _is_cuda:
     from sgl_kernel import concat_mla_absorb_q
 
 # Constants
-DEFAULT_WORKSPACE_SIZE_MB = 128  # Memory workspace size in MB
+DEFAULT_WORKSPACE_SIZE_MB = 150  # Memory workspace size in MB
 
 # Block constraint from flashinfer requirements
 # From flashinfer.decode._check_trtllm_gen_mla_shape:
@@ -194,6 +195,36 @@ def unpad_draft_extend_output_kernel(
     )
 
 
+def _quantize_fp8_qkv(q, k, v, layer):
+    q = q.to(torch.float8_e4m3fn)
+
+    k_scale = getattr(layer, "k_scale_float", None)
+    if k_scale is None:
+        k_scale = 1.0
+    if k_scale != 1.0:
+        assert hasattr(layer, "k_scale"), "k_scale is not set"
+        k_2d, _ = scaled_fp8_quant(
+            k.reshape(-1, k.shape[-1]).contiguous(), layer.k_scale
+        )
+        k = k_2d.reshape(k.shape)
+    else:
+        k = k.to(torch.float8_e4m3fn)
+
+    v_scale = getattr(layer, "v_scale_float", None)
+    if v_scale is None:
+        v_scale = 1.0
+    if v_scale != 1.0:
+        assert hasattr(layer, "v_scale"), "v_scale is not set"
+        v_2d, _ = scaled_fp8_quant(
+            v.reshape(-1, v.shape[-1]).contiguous(), layer.v_scale
+        )
+        v = v_2d.reshape(v.shape)
+    else:
+        v = v.to(torch.float8_e4m3fn)
+
+    return q, k, v, k_scale, v_scale
+
+
 global_zero_init_workspace_buffer = None
 
 
@@ -1035,6 +1066,25 @@ class TRTLLMMLABackend(FlashInferMLAAttnBackend):
             k = torch.cat([k, k_rope], dim=-1)
         k = k.view(-1, layer.tp_k_head_num, layer.head_dim)
         v = v.view(-1, layer.tp_k_head_num, layer.v_head_dim)
+
+        q_scale = k_scale = v_scale = 1.0
+        if self.data_type == torch.float8_e4m3fn:
+            q, k, v, k_scale, v_scale = _quantize_fp8_qkv(q, k, v, layer)
+
+        common_trtllm_args = {
+            "query": q,
+            "key": k,
+            "value": v,
+            "workspace_buffer": self.workspace_buffer,
+            "batch_size": forward_batch.batch_size,
+            "window_left": -1,
+            "enable_pdl": False,
+            "max_q_len": self.forward_prefill_metadata.max_seq_len,
+            "bmm1_scale": q_scale * k_scale * layer.scaling,
+            "bmm2_scale": v_scale,
+            "cum_seq_lens_q": self.forward_prefill_metadata.cum_seq_lens,
+        }
+
         # When chunked prefix cache is enabled, dispatch to different path for ragged attention.
         if forward_batch.attn_attend_prefix_cache:
             # MHA for chunked prefix kv cache when running model with MLA
@@ -1044,47 +1094,41 @@ class TRTLLMMLABackend(FlashInferMLAAttnBackend):
             assert k_rope is None
             chunk_idx = forward_batch.prefix_chunk_idx
 
-            output_shape = (q.shape[0], layer.tp_q_head_num, layer.v_head_dim)
+            out = torch.zeros(
+                q.shape[0],
+                layer.tp_q_head_num,
+                layer.v_head_dim,
+                dtype=self.q_data_type,
+                device=q.device,
+            )
             return flashinfer.prefill.trtllm_ragged_attention_deepseek(
-                query=q,
-                key=k,
-                value=v,
-                workspace_buffer=self.workspace_buffer,
+                **common_trtllm_args,
                 seq_lens=forward_batch.prefix_chunk_seq_lens[chunk_idx],
-                max_q_len=self.forward_prefill_metadata.max_seq_len,
                 max_kv_len=forward_batch.prefix_chunk_max_seq_lens[chunk_idx],
-                bmm1_scale=layer.scaling,
-                bmm2_scale=1.0,
                 o_sf_scale=-1.0,
-                batch_size=forward_batch.batch_size,
-                window_left=-1,
-                cum_seq_lens_q=self.forward_prefill_metadata.cum_seq_lens,
                 cum_seq_lens_kv=forward_batch.prefix_chunk_cu_seq_lens[chunk_idx],
-                enable_pdl=False,
                 is_causal=False,
                 return_lse=True,
-                out=torch.zeros(*output_shape, dtype=q.dtype, device=q.device),
+                out=out,
+            )
+        else:
+            out = torch.empty(
+                q.shape[0],
+                q.shape[1],
+                v.shape[2],
+                device=q.device,
+                dtype=self.q_data_type,
+            )
+            return flashinfer.prefill.trtllm_ragged_attention_deepseek(
+                **common_trtllm_args,
+                seq_lens=self.forward_prefill_metadata.seq_lens,
+                max_kv_len=self.forward_prefill_metadata.max_seq_len,
+                o_sf_scale=1.0,
+                cum_seq_lens_kv=self.forward_prefill_metadata.cum_seq_lens,
+                is_causal=True,
+                return_lse=forward_batch.mha_return_lse,
+                out=out,
             )
-
-        return flashinfer.prefill.trtllm_ragged_attention_deepseek(
-            query=q,
-            key=k,
-            value=v,
-            workspace_buffer=self.workspace_buffer,
-            seq_lens=self.forward_prefill_metadata.seq_lens,
-            max_q_len=self.forward_prefill_metadata.max_seq_len,
-            max_kv_len=self.forward_prefill_metadata.max_seq_len,
-            bmm1_scale=layer.scaling,
-            bmm2_scale=1.0,
-            o_sf_scale=1.0,
-            batch_size=forward_batch.batch_size,
-            window_left=-1,
-            cum_seq_lens_q=self.forward_prefill_metadata.cum_seq_lens,
-            cum_seq_lens_kv=self.forward_prefill_metadata.cum_seq_lens,
-            enable_pdl=False,
-            is_causal=True,
-            return_lse=forward_batch.mha_return_lse,
-        )
 
 
 class TRTLLMMLAMultiStepDraftBackend(FlashInferMLAMultiStepDraftBackend):