feat(diffusion): add request-gated VAE fast paths

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

vllm_omni/diffusion/vae_optimizations/optimize.py

@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Pipeline-level installation for optional VAE optimizations."""
+
+from __future__ import annotations
+
+from torch import nn
+from vllm.logger import init_logger
+
+from vllm_omni.diffusion.data import OmniDiffusionConfig
+from vllm_omni.diffusion.offloader.module_collector import ModuleDiscovery
+from vllm_omni.diffusion.vae_optimizations.image import maybe_optimize_image_vae
+from vllm_omni.diffusion.vae_optimizations.precision import configure_wan_decode_precision
+from vllm_omni.diffusion.vae_optimizations.wan import maybe_optimize_wan_vae
+from vllm_omni.platforms import current_omni_platform
+
+logger = init_logger(__name__)
+
+_FOLDED_CACHE_NAMES = (
+    "_fused_weight",
+    "_vllm_folded_value_weight",
+    "_vllm_folded_value_bias",
+)
+
+
+def optimize_pipeline_vaes(pipeline: nn.Module, od_config: OmniDiffusionConfig) -> None:
+    """Configure declared VAE components once after checkpoint loading."""
+
+    precision = getattr(od_config, "vae_decode_precision", None)
+    vaes = ModuleDiscovery.discover(pipeline).vaes
+    for vae in vaes:
+        # An explicit precision override is a serving contract, so failures on
+        # a recognized Wan VAE must abort startup instead of being hidden.
+        configure_wan_decode_precision(vae, precision)
+
+    if not current_omni_platform.is_cuda():
+        return
+
+    for vae in vaes:
+        for optimizer in (maybe_optimize_image_vae, maybe_optimize_wan_vae):
+            try:
+                optimizer(vae)
+            except Exception:
+                # A wrapper may already have installed its exact fallback
+                # before a later optional rewrite failed. With no registered
+                # enabled gate, those wrappers remain on the reference path.
+                logger.warning(
+                    "Failed to install optional VAE fast paths on %s; using the reference path",
+                    type(vae).__name__,
+                    exc_info=True,
+                )
+
+
+def clear_pipeline_vae_fast_path_caches(pipeline: nn.Module) -> None:
+    """Release lazily folded buffers before the worker enters sleep mode."""
+
+    cleared = 0
+    for vae in ModuleDiscovery.discover(pipeline).vaes:
+        if not getattr(vae, "_vllm_vae_fast_path_installed", False):
+            continue
+        for module in vae.modules():
+            for name in _FOLDED_CACHE_NAMES:
+                if name in module._buffers and module._buffers[name] is not None:
+                    setattr(module, name, None)
+                    cleared += 1
+    if cleared:
+        logger.debug("Released %d lazy VAE fast-path buffers before sleep", cleared)
+
+
+__all__ = ["clear_pipeline_vae_fast_path_caches", "optimize_pipeline_vaes"]