Partial Loading PR2: Add utils to support partial loading of models from CPU to GPU

invokeai/backend/model_manager/load/model_cache/cached_model/cached_model_only_full_load.py

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+from typing import Any
+
+import torch
+
+
+class CachedModelOnlyFullLoad:
+    """A wrapper around a PyTorch model to handle full loads and unloads between the CPU and the compute device.
+    Note: "VRAM" is used throughout this class to refer to the memory on the compute device. It could be CUDA memory,
+    MPS memory, etc.
+    """
+
+    def __init__(self, model: torch.nn.Module | Any, compute_device: torch.device, total_bytes: int):
+        """Initialize a CachedModelOnlyFullLoad.
+        Args:
+            model (torch.nn.Module | Any): The model to wrap. Should be on the CPU.
+            compute_device (torch.device): The compute device to move the model to.
+            total_bytes (int): The total size (in bytes) of all the weights in the model.
+        """
+        # model is often a torch.nn.Module, but could be any model type. Throughout this class, we handle both cases.
+        self._model = model
+        self._compute_device = compute_device
+        self._offload_device = torch.device("cpu")
+
+        # A CPU read-only copy of the model's state dict.
+        self._cpu_state_dict: dict[str, torch.Tensor] | None = None
+        if isinstance(model, torch.nn.Module):
+            self._cpu_state_dict = model.state_dict()
+
+        self._total_bytes = total_bytes
+        self._is_in_vram = False
+
+    @property
+    def model(self) -> torch.nn.Module:
+        return self._model
+
+    def get_cpu_state_dict(self) -> dict[str, torch.Tensor] | None:
+        """Get a read-only copy of the model's state dict in RAM."""
+        # TODO(ryand): Document this better.
+        return self._cpu_state_dict
+
+    def total_bytes(self) -> int:
+        """Get the total size (in bytes) of all the weights in the model."""
+        return self._total_bytes
+
+    def cur_vram_bytes(self) -> int:
+        """Get the size (in bytes) of the weights that are currently in VRAM."""
+        if self._is_in_vram:
+            return self._total_bytes
+        else:
+            return 0
+
+    def is_in_vram(self) -> bool:
+        """Return true if the model is currently in VRAM."""
+        return self._is_in_vram
+
+    def full_load_to_vram(self) -> int:
+        """Load all weights into VRAM (if supported by the model).
+        Returns:
+            The number of bytes loaded into VRAM.
+        """
+        if self._is_in_vram:
+            # Already in VRAM.
+            return 0
+
+        if not hasattr(self._model, "to"):
+            # Model doesn't support moving to a device.
+            return 0
+
+        if self._cpu_state_dict is not None:
+            new_state_dict: dict[str, torch.Tensor] = {}
+            for k, v in self._cpu_state_dict.items():
+                new_state_dict[k] = v.to(self._compute_device, copy=True)
+            self._model.load_state_dict(new_state_dict, assign=True)
+        self._model.to(self._compute_device)
+
+        self._is_in_vram = True
+        return self._total_bytes
+
+    def full_unload_from_vram(self) -> int:
+        """Unload all weights from VRAM.
+        Returns:
+            The number of bytes unloaded from VRAM.
+        """
+        if not self._is_in_vram:
+            # Already in RAM.
+            return 0
+
+        if self._cpu_state_dict is not None:
+            self._model.load_state_dict(self._cpu_state_dict, assign=True)
+        self._model.to(self._offload_device)
+
+        self._is_in_vram = False
+        return self._total_bytes

invokeai/backend/model_manager/load/model_cache/cached_model/cached_model_with_partial_load.py

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+import torch
+
+from invokeai.backend.model_manager.load.model_cache.torch_module_autocast.torch_module_autocast import (
+    AUTOCAST_MODULE_TYPE_MAPPING,
+    apply_custom_layers_to_model,
+    remove_custom_layers_from_model,
+)
+from invokeai.backend.util.calc_tensor_size import calc_tensor_size
+from invokeai.backend.util.logging import InvokeAILogger
+
+
+def set_nested_attr(obj: object, attr: str, value: object):
+    """A helper function that extends setattr() to support nested attributes.
+
+    Example:
+        set_nested_attr(model, "module.encoder.conv1.weight", new_conv1_weight)
+    """
+    attrs = attr.split(".")
+    for attr in attrs[:-1]:
+        obj = getattr(obj, attr)
+    setattr(obj, attrs[-1], value)
+
+
+class CachedModelWithPartialLoad:
+    """A wrapper around a PyTorch model to handle partial loads and unloads between the CPU and the compute device.
+
+    Note: "VRAM" is used throughout this class to refer to the memory on the compute device. It could be CUDA memory,
+    MPS memory, etc.
+    """
+
+    def __init__(self, model: torch.nn.Module, compute_device: torch.device):
+        self._model = model
+        self._compute_device = compute_device
+
+        # A CPU read-only copy of the model's state dict.
+        self._cpu_state_dict: dict[str, torch.Tensor] = model.state_dict()
+
+        # TODO(ryand): Handle the case where the model sizes changes after initial load (e.g. due to dtype casting).
+        # Consider how we should handle this for both self._total_bytes and self._cur_vram_bytes.
+        self._total_bytes = sum(calc_tensor_size(p) for p in self._cpu_state_dict.values())
+        self._cur_vram_bytes: int | None = None
+
+        self._modules_that_support_autocast = self._find_modules_that_support_autocast()
+        self._keys_in_modules_that_do_not_support_autocast = self._find_keys_in_modules_that_do_not_support_autocast()
+
+    def _find_modules_that_support_autocast(self) -> dict[str, torch.nn.Module]:
+        """Find all modules that support autocasting."""
+        return {n: m for n, m in self._model.named_modules() if type(m) in AUTOCAST_MODULE_TYPE_MAPPING}
+
+    def _find_keys_in_modules_that_do_not_support_autocast(self) -> set[str]:
+        keys_in_modules_that_do_not_support_autocast = set()
+        for key in self._cpu_state_dict.keys():
+            for module_name in self._modules_that_support_autocast.keys():
+                if key.startswith(module_name):
+                    break
+            else:
+                keys_in_modules_that_do_not_support_autocast.add(key)
+        return keys_in_modules_that_do_not_support_autocast
+
+    def _move_non_persistent_buffers_to_device(self, device: torch.device):
+        """Move the non-persistent buffers to the target device. These buffers are not included in the state dict,
+        so we need to move them manually.
+        """
+        # HACK(ryand): Typically, non-persistent buffers are moved when calling module.to(device). We don't move entire
+        # modules, because we manage the devices of individual tensors using the state dict. Since non-persistent
+        # buffers are not included in the state dict, we need to handle them manually. The only way to do this is by
+        # using private torch.nn.Module attributes.
+        for module in self._model.modules():
+            for name, buffer in module.named_buffers():
+                if name in module._non_persistent_buffers_set:
+                    module._buffers[name] = buffer.to(device, copy=True)
+
+    @property
+    def model(self) -> torch.nn.Module:
+        return self._model
+
+    def get_cpu_state_dict(self) -> dict[str, torch.Tensor] | None:
+        """Get a read-only copy of the model's state dict in RAM."""
+        # TODO(ryand): Document this better.
+        return self._cpu_state_dict
+
+    def total_bytes(self) -> int:
+        """Get the total size (in bytes) of all the weights in the model."""
+        return self._total_bytes
+
+    def cur_vram_bytes(self) -> int:
+        """Get the size (in bytes) of the weights that are currently in VRAM."""
+        if self._cur_vram_bytes is None:
+            cur_state_dict = self._model.state_dict()
+            self._cur_vram_bytes = sum(
+                calc_tensor_size(p) for p in cur_state_dict.values() if p.device.type == self._compute_device.type
+            )
+        return self._cur_vram_bytes
+
+    def full_load_to_vram(self) -> int:
+        """Load all weights into VRAM."""
+        return self.partial_load_to_vram(self.total_bytes())
+
+    def full_unload_from_vram(self) -> int:
+        """Unload all weights from VRAM."""
+        return self.partial_unload_from_vram(self.total_bytes())
+
+    @torch.no_grad()
+    def partial_load_to_vram(self, vram_bytes_to_load: int) -> int:
+        """Load more weights into VRAM without exceeding vram_bytes_to_load.
+
+        Returns:
+            The number of bytes loaded into VRAM.
+        """
+        # TODO(ryand): Handle the case where an exception is thrown while loading or unloading weights. At the very
+        # least, we should reset self._cur_vram_bytes to None.
+
+        vram_bytes_loaded = 0
+
+        cur_state_dict = self._model.state_dict()
+
+        # First, process the keys *must* be loaded into VRAM.
+        for key in self._keys_in_modules_that_do_not_support_autocast:
+            param = cur_state_dict[key]
+            if param.device.type == self._compute_device.type:
+                continue
+
+            param_size = calc_tensor_size(param)
+            cur_state_dict[key] = param.to(self._compute_device, copy=True)
+            vram_bytes_loaded += param_size
+
+        if vram_bytes_loaded > vram_bytes_to_load:
+            logger = InvokeAILogger.get_logger()
+            logger.warning(
+                f"Loaded {vram_bytes_loaded / 2**20} MB into VRAM, but only {vram_bytes_to_load / 2**20} MB were "
+                "requested. This is the minimum set of weights in VRAM required to run the model."
+            )
+
+        # Next, process the keys that can optionally be loaded into VRAM.
+        fully_loaded = True
+        for key, param in cur_state_dict.items():
+            if param.device.type == self._compute_device.type:
+                continue
+
+            param_size = calc_tensor_size(param)
+            if vram_bytes_loaded + param_size > vram_bytes_to_load:
+                # TODO(ryand): Should we just break here? If we couldn't fit this parameter into VRAM, is it really
+                # worth continuing to search for a smaller parameter that would fit?
+                fully_loaded = False
+                continue
+
+            cur_state_dict[key] = param.to(self._compute_device, copy=True)
+            vram_bytes_loaded += param_size
+
+        if vram_bytes_loaded > 0:
+            # We load the entire state dict, not just the parameters that changed, in case there are modules that
+            # override _load_from_state_dict() and do some funky stuff that requires the entire state dict.
+            # Alternatively, in the future, grouping parameters by module could probably solve this problem.
+            self._model.load_state_dict(cur_state_dict, assign=True)
+
+        if self._cur_vram_bytes is not None:
+            self._cur_vram_bytes += vram_bytes_loaded
+
+        if fully_loaded:
+            remove_custom_layers_from_model(self._model)
+            # TODO(ryand): Warn if the self.cur_vram_bytes() and self.total_bytes() are out of sync.
+        else:
+            apply_custom_layers_to_model(self._model)
+
+        # Move all non-persistent buffers to the compute device. These are a weird edge case and do not participate in
+        # the vram_bytes_loaded tracking.
+        self._move_non_persistent_buffers_to_device(self._compute_device)
+
+        return vram_bytes_loaded
+
+    @torch.no_grad()
+    def partial_unload_from_vram(self, vram_bytes_to_free: int) -> int:
+        """Unload weights from VRAM until vram_bytes_to_free bytes are freed. Or the entire model is unloaded.
+
+        Returns:
+            The number of bytes unloaded from VRAM.
+        """
+        vram_bytes_freed = 0
+
+        offload_device = "cpu"
+        cur_state_dict = self._model.state_dict()
+        for key, param in cur_state_dict.items():
+            if vram_bytes_freed >= vram_bytes_to_free:
+                break
+
+            if param.device.type == offload_device:
+                continue
+
+            cur_state_dict[key] = self._cpu_state_dict[key]
+            vram_bytes_freed += calc_tensor_size(param)
+
+        if vram_bytes_freed > 0:
+            self._model.load_state_dict(cur_state_dict, assign=True)
+
+        if self._cur_vram_bytes is not None:
+            self._cur_vram_bytes -= vram_bytes_freed
+
+        # We may have gone from a fully-loaded model to a partially-loaded model, so we need to reapply the custom
+        # layers.
+        apply_custom_layers_to_model(self._model)
+        return vram_bytes_freed

invokeai/backend/model_manager/load/model_cache/torch_module_autocast/autocast_modules.py

@@ -0,0 +1,50 @@
+import torch
+
+from invokeai.backend.model_manager.load.model_cache.torch_module_autocast.cast_to_device import cast_to_device
+
+# This file contains custom torch.nn.Module classes that support streaming of weights to the target device.
+# Each class sub-classes the original module type that is is replacing, so the following properties are preserved:
+# - isinstance(m, torch.nn.OrginalModule) should still work.
+# - Patching the weights (e.g. for LoRA) should still work if non-quantized.
+
+
+class CustomLinear(torch.nn.Linear):
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        weight = cast_to_device(self.weight, input.device)
+        bias = cast_to_device(self.bias, input.device)
+        return torch.nn.functional.linear(input, weight, bias)
+
+
+class CustomConv1d(torch.nn.Conv1d):
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        weight = cast_to_device(self.weight, input.device)
+        bias = cast_to_device(self.bias, input.device)
+        return self._conv_forward(input, weight, bias)
+
+
+class CustomConv2d(torch.nn.Conv2d):
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        weight = cast_to_device(self.weight, input.device)
+        bias = cast_to_device(self.bias, input.device)
+        return self._conv_forward(input, weight, bias)
+
+
+class CustomGroupNorm(torch.nn.GroupNorm):
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        weight = cast_to_device(self.weight, input.device)
+        bias = cast_to_device(self.bias, input.device)
+        return torch.nn.functional.group_norm(input, self.num_groups, weight, bias, self.eps)
+
+
+class CustomEmbedding(torch.nn.Embedding):
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        weight = cast_to_device(self.weight, input.device)
+        return torch.nn.functional.embedding(
+            input,
+            weight,
+            self.padding_idx,
+            self.max_norm,
+            self.norm_type,
+            self.scale_grad_by_freq,
+            self.sparse,
+        )

invokeai/backend/model_manager/load/model_cache/torch_module_autocast/cast_to_device.py

@@ -0,0 +1,15 @@
+from typing import TypeVar
+
+import torch
+
+T = TypeVar("T", torch.Tensor, None, torch.Tensor | None)
+
+
+def cast_to_device(t: T, to_device: torch.device) -> T:
+    """Helper function to cast an optional tensor to a target device."""
+    if t is None:
+        return t
+
+    if t.device.type != to_device.type:
+        return t.to(to_device)
+    return t

invokeai/backend/model_manager/load/model_cache/torch_module_autocast/custom_invoke_linear_8_bit_lt.py

@@ -0,0 +1,27 @@
+import bitsandbytes as bnb
+import torch
+
+from invokeai.backend.model_manager.load.model_cache.torch_module_autocast.cast_to_device import cast_to_device
+from invokeai.backend.quantization.bnb_llm_int8 import InvokeLinear8bitLt
+
+
+class CustomInvokeLinear8bitLt(InvokeLinear8bitLt):
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        matmul_state = bnb.MatmulLtState()
+        matmul_state.threshold = self.state.threshold
+        matmul_state.has_fp16_weights = self.state.has_fp16_weights
+        matmul_state.use_pool = self.state.use_pool
+        matmul_state.is_training = self.training
+        # The underlying InvokeInt8Params weight must already be quantized.
+        assert self.weight.CB is not None
+        matmul_state.CB = cast_to_device(self.weight.CB, x.device)
+        matmul_state.SCB = cast_to_device(self.weight.SCB, x.device)
+
+        # weights are cast automatically as Int8Params, but the bias has to be cast manually.
+        if self.bias is not None and self.bias.dtype != x.dtype:
+            self.bias.data = self.bias.data.to(x.dtype)
+
+        # NOTE(ryand): The second parameter should not be needed at all given our expected inference configuration, but
+        # it's dtype field must be accessible, even though it's not used. We pass in self.weight even though it could be
+        # on the wrong device.
+        return bnb.matmul(x, self.weight, bias=cast_to_device(self.bias, x.device), state=matmul_state)