Speedup model init on CPU (by 10x+ for llama-3-8B as one example) (#31771)

* 1,100%!

* Clean

* Don't touch DS

* Experiment with dtype allocation

* skip test_load_save_without_tied_weights test

* A little faster

* Include proper upscaling?

* Fixup tests

* Potentially skip?

* Let's see if this fixes git history

* Maintain new dtype

* Fin

* Rm hook idea for now

* New approach, see what breaks

* stage

* Clean

* Stash

* Should be fin now, just need to mark failing models

* Clean up

* Simplify

* Deal with weird models

* Enc/Dec

* Skip w/ reason

* Adjust test

* Fix test

* one more test

* Keep experimenting

* Fix ref

* TO REMOVE: testing feedback CI

* Right push

* Update tests/utils/test_modeling_utils.py

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* disable

* Add new func

* Test nits from Amy

* Update src/transformers/modeling_utils.py

Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

* Adjust comment

* Adjust comment on skip

* make private

* Fin

* Should be a not flag

* Clarify and rename test

---------

Co-authored-by: Marc Sun <marc@huggingface.co>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

docs/source/en/main_classes/model.md

@@ -40,6 +40,10 @@ for text generation, [`~generation.GenerationMixin`] (for the PyTorch models),
     - push_to_hub
     - all
 
+Custom models should also include a `_supports_assign_param_buffer`, which determines if superfast init can apply
+on the particular model. Signs that your model needs this are if `test_save_and_load_from_pretrained` fails. If so,
+set this to `False`.
+
 ## ModuleUtilsMixin
 
 [[autodoc]] modeling_utils.ModuleUtilsMixin

src/transformers/modeling_utils.py

@@ -338,6 +338,32 @@ def dtype_byte_size(dtype):
     return bit_size // 8
 
 
+def check_support_param_buffer_assignment(model_to_load, state_dict, start_prefix=""):
+    """
+    Checks if `model_to_load` supports param buffer assignment (such
+    as when loading in empty weights) by first checking
+    if the model explicitly disables it, then by ensuring that the state dict keys
+    are a subset of the model's parameters.
+    """
+    if len([key for key in state_dict if key.startswith(start_prefix)]) == 0:
+        return False
+
+    # Some models explicitly do not support param buffer assignment
+    if not getattr(model_to_load, "_supports_param_buffer_assignment", False):
+        logger.debug(
+            f"{model_to_load.__class__.__name__} does not support param buffer assignment, loading will be slower"
+        )
+        return False
+
+    # If the model does, the incoming `state_dict` and the `model_to_load` must be the same dtype
+    first_key = list(model_to_load.state_dict().keys())[0]
+    if start_prefix + first_key in state_dict:
+        return state_dict[start_prefix + first_key].dtype == model_to_load.state_dict()[first_key].dtype
+
+    # For cases when the `state_dict` doesn't contain real weights to the model (`test_model_weights_reload_no_missing_tied_weights`)
+    return False
+
+
 def shard_checkpoint(
     state_dict: Dict[str, torch.Tensor], max_shard_size: Union[int, str] = "10GB", weights_name: str = WEIGHTS_NAME
 ):
@@ -657,7 +683,7 @@ def _find_identical(tensors: List[Set[str]], state_dict: Dict[str, torch.Tensor]
     return shared_tensors, identical
 
 
-def _load_state_dict_into_model(model_to_load, state_dict, start_prefix):
+def _load_state_dict_into_model(model_to_load, state_dict, start_prefix, assign_to_params_buffers=False):
     # Convert old format to new format if needed from a PyTorch state_dict
     old_keys = []
     new_keys = []
@@ -685,8 +711,10 @@ def _load_state_dict_into_model(model_to_load, state_dict, start_prefix):
 
     # PyTorch's `_load_from_state_dict` does not copy parameters in a module's descendants
     # so we need to apply the function recursively.
-    def load(module: nn.Module, state_dict, prefix=""):
+    def load(module: nn.Module, state_dict, prefix="", assign_to_params_buffers=False):
         local_metadata = {} if metadata is None else metadata.get(prefix[:-1], {})
+        local_metadata["assign_to_params_buffers"] = assign_to_params_buffers
+
         args = (state_dict, prefix, local_metadata, True, [], [], error_msgs)
         # Parameters of module and children will start with prefix. We can exit early if there are none in this
         # state_dict
@@ -710,9 +738,9 @@ def _load_state_dict_into_model(model_to_load, state_dict, start_prefix):
 
         for name, child in module._modules.items():
             if child is not None:
-                load(child, state_dict, prefix + name + ".")
+                load(child, state_dict, prefix + name + ".", assign_to_params_buffers)
 
-    load(model_to_load, state_dict, prefix=start_prefix)
+    load(model_to_load, state_dict, prefix=start_prefix, assign_to_params_buffers=assign_to_params_buffers)
     # Delete `state_dict` so it could be collected by GC earlier. Note that `state_dict` is a copy of the argument, so
     # it's safe to delete it.
     del state_dict
@@ -2852,6 +2880,10 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
         The warning *Weights from XXX not used in YYY* means that the layer XXX is not used by YYY, therefore those
         weights are discarded.
 
+        If model weights are the same precision as the base model (and is a supported model), weights will be lazily loaded
+        in using the `meta` device and brought into memory once an input is passed through that layer regardless of
+        `low_cpu_mem_usage`.
+
         Parameters:
             pretrained_model_name_or_path (`str` or `os.PathLike`, *optional*):
                 Can be either:
@@ -2952,7 +2984,13 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
 
             low_cpu_mem_usage(`bool`, *optional*):
                 Tries to not use more than 1x model size in CPU memory (including peak memory) while loading the model.
+                Generally should be combined with a `device_map` (such as `"auto"`) for best results.
                 This is an experimental feature and a subject to change at any moment.
+                </Tip>
+                    If the model weights are in the same precision as the model loaded in, `low_cpu_mem_usage` (without
+                    `device_map`) is redundant and will not provide any benefit in regards to CPU memory usage. However,
+                    this should still be enabled if you are passing in a `device_map`.
+                </Tip>
             torch_dtype (`str` or `torch.dtype`, *optional*):
                 Override the default `torch.dtype` and load the model under a specific `dtype`. The different options
                 are:
@@ -4018,6 +4056,7 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
 
         missing_keys = sorted(set(expected_keys) - set(loaded_keys))
         unexpected_keys = set(loaded_keys) - set(expected_keys)
+
         # Remove nonpersistent buffers from unexpected keys: they are not in the state dict but will be in the model
         # buffers
         model_buffers = {n for n, _ in model.named_buffers()}
@@ -4252,7 +4291,12 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
                 )
             else:
                 # Sharded checkpoint or whole but low_cpu_mem_usage==True
-                error_msgs = _load_state_dict_into_model(model_to_load, state_dict, start_prefix)
+                assign_to_params_buffers = check_support_param_buffer_assignment(
+                    model_to_load, state_dict, start_prefix
+                )
+                error_msgs = _load_state_dict_into_model(
+                    model_to_load, state_dict, start_prefix, assign_to_params_buffers
+                )
 
         else:
             # This should always be a list but, just to be sure.
@@ -4280,6 +4324,7 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
 
             if len(resolved_archive_file) > 1:
                 resolved_archive_file = logging.tqdm(resolved_archive_file, desc="Loading checkpoint shards")
+            assign_to_params_buffers = None
             for shard_file in resolved_archive_file:
                 # Skip the load for shards that only contain disk-offloaded weights when using safetensors for the offload.
                 if shard_file in disk_only_shard_files:
@@ -4323,7 +4368,14 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
                         )
                         error_msgs += new_error_msgs
                 else:
-                    error_msgs += _load_state_dict_into_model(model_to_load, state_dict, start_prefix)
+                    # Sharded checkpoint or whole but low_cpu_mem_usage==True
+                    if assign_to_params_buffers is None:
+                        assign_to_params_buffers = check_support_param_buffer_assignment(
+                            model_to_load, state_dict, start_prefix
+                        )
+                    error_msgs += _load_state_dict_into_model(
+                        model_to_load, state_dict, start_prefix, assign_to_params_buffers
+                    )
 
                 # force memory release
                 del state_dict

src/transformers/models/encoder_decoder/modeling_encoder_decoder.py

@@ -178,6 +178,7 @@ class EncoderDecoderModel(PreTrainedModel):
     base_model_prefix = "encoder_decoder"
     main_input_name = "input_ids"
     supports_gradient_checkpointing = True
+    _supports_param_buffer_assignment = False
 
     def __init__(
         self,

src/transformers/models/lxmert/modeling_lxmert.py

@@ -773,6 +773,7 @@ class LxmertPreTrainedModel(PreTrainedModel):
     config_class = LxmertConfig
     load_tf_weights = load_tf_weights_in_lxmert
     base_model_prefix = "lxmert"
+    _supports_param_buffer_assignment = False
 
     def _init_weights(self, module):
         """Initialize the weights"""

src/transformers/models/vision_encoder_decoder/modeling_vision_encoder_decoder.py

@@ -159,6 +159,7 @@ class VisionEncoderDecoderModel(PreTrainedModel):
     base_model_prefix = "vision_encoder_decoder"
     main_input_name = "pixel_values"
     supports_gradient_checkpointing = True
+    _supports_param_buffer_assignment = False
 
     def __init__(
         self,

tests/models/bart/test_modeling_bart.py

@@ -512,6 +512,12 @@ class BartModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMixin
         model.generate(input_ids, attention_mask=attention_mask)
         model.generate(num_beams=4, do_sample=True, early_stopping=False, num_return_sequences=3)
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""

tests/models/bigbird_pegasus/test_modeling_bigbird_pegasus.py

@@ -476,6 +476,12 @@ class BigBirdPegasusModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineT
 
         self.assertTrue(torch.allclose(outputs1, outputs2, atol=1e-5))
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 @require_sentencepiece

tests/models/longt5/test_modeling_longt5.py

@@ -758,6 +758,12 @@ class LongT5ModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
             [encoder_expected_shape] * len(attentions),
         )
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 class LongT5TGlobalModelTest(LongT5ModelTest):
@@ -1097,6 +1103,12 @@ class LongT5EncoderOnlyModelTest(ModelTesterMixin, unittest.TestCase):
                     [self.model_tester.num_attention_heads, block_len, 3 * block_len],
                 )
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 class LongT5EncoderOnlyTGlobalModelTest(LongT5EncoderOnlyModelTest):
     def setUp(self):

tests/models/lxmert/test_modeling_lxmert.py

@@ -778,6 +778,12 @@ class LxmertModelTest(ModelTesterMixin, PipelineTesterMixin, unittest.TestCase):
     def test_save_load_low_cpu_mem_usage_no_safetensors(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 class LxmertModelIntegrationTest(unittest.TestCase):

tests/models/m2m_100/test_modeling_m2m_100.py

@@ -331,6 +331,12 @@ class M2M100ModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
         model.generate(input_ids, attention_mask=attention_mask)
         model.generate(num_beams=4, do_sample=True, early_stopping=False, num_return_sequences=3)
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 def _long_tensor(tok_lst):
     return torch.tensor(tok_lst, dtype=torch.long, device=torch_device)

tests/models/mbart/test_modeling_mbart.py

@@ -369,6 +369,12 @@ class MBartModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMixi
             2,
         )
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""

tests/models/nllb_moe/test_modeling_nllb_moe.py

@@ -346,6 +346,12 @@ class NllbMoeModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMi
         self.assertIsNotNone(model(**input_dict)["encoder_router_logits"][1])
         self.assertIsNotNone(model(**input_dict)["decoder_router_logits"][0])
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 @require_sentencepiece

tests/models/plbart/test_modeling_plbart.py

@@ -323,6 +323,12 @@ class PLBartModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMix
     def test_sample_generate(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""

tests/models/seamless_m4t/test_modeling_seamless_m4t.py

@@ -506,6 +506,12 @@ class SeamlessM4TModelWithSpeechInputTest(ModelTesterMixin, unittest.TestCase):
     def test_training_gradient_checkpointing_use_reentrant_false(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
     def test_attention_outputs(self):
         # expected length is subsampled so need to change a bit this test
         if not self.has_attentions:
@@ -758,6 +764,12 @@ class SeamlessM4TModelWithTextInputTest(
     def test_retain_grad_hidden_states_attentions(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 class SeamlessM4TGenerationTest(unittest.TestCase):

tests/models/seamless_m4t_v2/test_modeling_seamless_m4t_v2.py

@@ -522,6 +522,12 @@ class SeamlessM4Tv2ModelWithSpeechInputTest(ModelTesterMixin, unittest.TestCase)
     def test_training_gradient_checkpointing_use_reentrant_false(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
     def test_attention_outputs(self):
         # expected length is subsampled so need to change a bit this test
         if not self.has_attentions:
@@ -748,6 +754,12 @@ class SeamlessM4Tv2ModelWithTextInputTest(ModelTesterMixin, GenerationTesterMixi
     def test_training_gradient_checkpointing_use_reentrant_false(self):
         pass
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 @require_torch
 class SeamlessM4Tv2GenerationTest(unittest.TestCase):

tests/models/switch_transformers/test_modeling_switch_transformers.py

@@ -720,6 +720,12 @@ class SwitchTransformersModelTest(ModelTesterMixin, GenerationTesterMixin, Pipel
             attn_weights = out[attn_name] if attn_name == attention_names[0] else out[attn_name][-1]
             self.assertEqual(sum([w.sum().item() for w in attn_weights]), 0.0)
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 class SwitchTransformersEncoderOnlyModelTester:
     def __init__(
@@ -843,6 +849,12 @@ class SwitchTransformersEncoderOnlyModelTest(ModelTesterMixin, unittest.TestCase
         config_and_inputs = self.model_tester.prepare_config_and_inputs()
         self.model_tester.create_and_check_model_fp16_forward(*config_and_inputs)
 
+    @unittest.skip(
+        reason="This architecure has tied weights by default and there is no way to remove it, check: https://github.com/huggingface/transformers/pull/31771#issuecomment-2210915245"
+    )
+    def test_load_save_without_tied_weights(self):
+        pass
+
 
 def use_task_specific_params(model, task):
     model.config.update(model.config.task_specific_params[task])

tests/utils/test_modeling_utils.py

@@ -20,6 +20,7 @@ import os.path
 import sys
 import tempfile
 import threading
+import time
 import unittest
 import unittest.mock as mock
 import uuid
@@ -894,32 +895,42 @@ class ModelUtilsTest(TestCasePlus):
     @require_usr_bin_time
     @require_accelerate
     @mark.accelerate_tests
-    def test_from_pretrained_low_cpu_mem_usage_measured(self):
-        # test that `from_pretrained(..., low_cpu_mem_usage=True)` uses less cpu memory than default
+    def test_from_pretrained_low_cpu_mem_usage_slower(self):
+        # Before this would test that `from_pretrained(..., low_cpu_mem_usage=True)` uses less cpu memory than default
+        # Now though the memory is the same, we simply test that loading with `low_cpu_mem_usage` winds up being *slower*
+        # (mostly from extra logic needed)
 
-        mname = "google-bert/bert-base-cased"
+        mname = "hf-internal-testing/tiny-random-bert"
 
         preamble = "from transformers import AutoModel"
         one_liner_str = f'{preamble}; AutoModel.from_pretrained("{mname}", low_cpu_mem_usage=False)'
+        start_time = time.time()
+        # Save this output as `max_rss_normal` if testing memory results
         max_rss_normal = self.python_one_liner_max_rss(one_liner_str)
+        end_time = time.time()
+        elapsed_time_normal = end_time - start_time
         # print(f"{max_rss_normal=}")
 
         one_liner_str = f'{preamble};  AutoModel.from_pretrained("{mname}", low_cpu_mem_usage=True)'
+        start_time = time.time()
+        # Save this output as `max_rss_low_mem` if testing memory results
         max_rss_low_mem = self.python_one_liner_max_rss(one_liner_str)
-        # print(f"{max_rss_low_mem=}")
+        end_time = time.time()
+        elapsed_time_low_mem = end_time - start_time
 
-        diff_bytes = max_rss_normal - max_rss_low_mem
-        diff_percent = diff_bytes / max_rss_low_mem
-        # print(f"{diff_bytes=}, {diff_percent=}")
-        # ideally we would compare that the diff is close to ~1x checkpoint size in bytes, but
-        # measuring cpu memory on linux is very tricky and inconsistent, so instead let's check that
-        # it's at least 15% less cpu memory consumed
+        # Should be within 2MBs of each other (overhead)
+        self.assertAlmostEqual(
+            max_rss_normal / 1024 / 1024,
+            max_rss_low_mem / 1024 / 1024,
+            delta=2,
+            msg="using `low_cpu_mem_usage` should incur the same memory usage in both cases.",
+        )
 
         self.assertGreater(
-            diff_percent,
-            0.15,
-            "should use less CPU memory for low_cpu_mem_usage=True, "
-            f"but got max_rss_normal={max_rss_normal} and max_rss_low_mem={max_rss_low_mem}",
+            elapsed_time_low_mem,
+            elapsed_time_normal,
+            "using `low_cpu_mem_usage` should be slower due to extra logic, "
+            f"but got elapsed_time_normal={elapsed_time_normal} and elapsed_time_low_mem={elapsed_time_low_mem}",
         )
 
         # if you want to compare things manually, let's first look at the size of the model in bytes