Add flash attention for sd3 medium

Signed-off-by: lijian <lijian6@sugon.com>

src/diffusers/models/attention.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 from typing import Any, Dict, Optional
 
+import os
 import torch
 import torch.nn.functional as F
 from torch import nn
@@ -119,7 +120,7 @@ class JointTransformerBlock(nn.Module):
                 f"Unknown context_norm_type: {context_norm_type}, currently only support `ada_norm_continous`, `ada_norm_zero`"
             )
         if hasattr(F, "scaled_dot_product_attention"):
-            processor = JointAttnProcessor2_0()
+            self.processor = JointAttnProcessor2_0()
         else:
             raise ValueError(
                 "The current PyTorch version does not support the `scaled_dot_product_attention` function."
@@ -133,7 +134,7 @@ class JointTransformerBlock(nn.Module):
             out_dim=attention_head_dim,
             context_pre_only=context_pre_only,
             bias=True,
-            processor=processor,
+            processor=self.processor,
         )
 
         self.norm2 = nn.LayerNorm(dim, elementwise_affine=False, eps=1e-6)
@@ -169,6 +170,9 @@ class JointTransformerBlock(nn.Module):
             )
 
         # Attention.
+        use_xformers = os.getenv('USE_XFORMERS', '0')
+        if use_xformers == '1':
+            self.attn.set_processor(self.processor)
         attn_output, context_attn_output = self.attn(
             hidden_states=norm_hidden_states, encoder_hidden_states=norm_encoder_hidden_states
         )

src/diffusers/models/attention_processor.py

@@ -16,6 +16,7 @@ import math
 from importlib import import_module
 from typing import Callable, List, Optional, Union
 
+import os
 import torch
 import torch.nn.functional as F
 from torch import nn
@@ -25,6 +26,7 @@ from ..utils import deprecate, logging
 from ..utils.import_utils import is_torch_npu_available, is_xformers_available
 from ..utils.torch_utils import maybe_allow_in_graph
 from .lora import LoRALinearLayer
+from xformers.ops import MemoryEfficientAttentionFlashAttentionOp, MemoryEfficientAttentionTritonFwdFlashBwOp
 
 
 logger = logging.get_logger(__name__)  # pylint: disable=invalid-name
@@ -1127,6 +1129,18 @@ class JointAttnProcessor2_0:
         key = torch.cat([key, encoder_hidden_states_key_proj], dim=1)
         value = torch.cat([value, encoder_hidden_states_value_proj], dim=1)
 
+        use_xformers = os.getenv('USE_XFORMERS', '0')
+        if use_xformers == '1':
+            query = attn.head_to_batch_dim(query).contiguous()
+            key = attn.head_to_batch_dim(key).contiguous()
+            value = attn.head_to_batch_dim(value).contiguous()
+
+            hidden_states = xformers.ops.memory_efficient_attention(
+                query, key, value, op=MemoryEfficientAttentionTritonFwdFlashBwOp
+            )
+            hidden_states = hidden_states.to(query.dtype)
+            hidden_states = attn.batch_to_head_dim(hidden_states)
+        else:
             inner_dim = key.shape[-1]
             head_dim = inner_dim // attn.heads
             query = query.view(batch_size, -1, attn.heads, head_dim).transpose(1, 2)

src/diffusers/pipelines/stable_diffusion_3/pipeline_stable_diffusion_3.py

@@ -36,7 +36,7 @@ from ...utils import (
 from ...utils.torch_utils import randn_tensor
 from ..pipeline_utils import DiffusionPipeline
 from .pipeline_output import StableDiffusion3PipelineOutput
-
+import os
 
 if is_torch_xla_available():
     import torch_xla.core.xla_model as xm
@@ -868,6 +868,9 @@ class StableDiffusion3Pipeline(DiffusionPipeline, SD3LoraLoaderMixin, FromSingle
                 if XLA_AVAILABLE:
                     xm.mark_step()
 
+        use_xformers = os.getenv('USE_XFORMERS', '0')
+        if use_xformers == '1':
+            self.disable_xformers_memory_efficient_attention()
         if output_type == "latent":
             image = latents