from enum import Enum from os import stat from typing import Dict, Optional, Tuple import torch import torch.distributed as dist import torch.nn as nn from colossalai.amp.naive_amp.grad_scaler import DynamicGradScaler from colossalai.context.parallel_mode import ParallelMode from colossalai.core import global_context as gpc from colossalai.logging import get_dist_logger from colossalai.nn.optimizer import ColossalaiOptimizer from colossalai.gemini.tensor_utils import (colo_model_data_tensor_move_inline, colo_tensor_mem_usage) from colossalai.zero.sharded_model import ShardedModelV2 from colossalai.zero.sharded_model._utils import cast_tensor_to_fp32 from torch import Tensor from torch.distributed import ProcessGroup from torch.nn.parameter import Parameter from torch.optim import Optimizer from colossalai.gemini.stateful_tensor import (StatefulTensor, TensorState) from colossalai.gemini.tensor_placement_policy import AutoTensorPlacementPolicy class OptimState(Enum): SCALED = 1 UNSCALED = 2 class ShardedOptimizerV2(ColossalaiOptimizer): """A wrapper for optimizer. ``ShardedOptimizerV2`` and ``ShardedModelV2`` implement Zero Redundancy Optimizer (ZeRO). By default the ZeRO optimizer stage 3 offload Optimizer States on CPU. We apply the Device-aware Operator Placement technique for OS placement from the following paper. `PatrickStar: Parallel Training of Pre-trained Models via Chunk-based Memory Management`_ GPU margin space is the remaining space after removing peak non-model data from the overall GPU memory, which is detected by a runtime memory tracer. We place as many OS chunks in the margin space as possible. The size of margin space can be controlled by ``gpu_margin_mem_ratio``. If it is set as ``0.0``, it is the same as classical ZeRO optimizer. Note: You must use ``ShardedOptimizerV2`` with ``ShardedModelV2``. Note: Make sure you set ``tensor_placement_policy`` in ``ShardedModelV2`` to `"auto"`, if you set ``gpu_margin_mem_ratio > 0``. Args: sharded_model (ShardedModelV2): A sharded model initialized by class ShardedModelV2. The optimizer will use the shard strategy provided by sharded model to shard param fp32 tensors. optimizer (Optimizer): An Optimizer instance. gpu_margin_mem_ratio (float, optional): The ratio of GPU remaining memory (after the first forward-backward) which will be used when using hybrid CPU optimizer. This argument is meaningless when `tensor_placement_policy` of `ShardedModelV2` is not "auto". Defaults to 0.0. initial_scale (float, optional): Initial scale used by DynamicGradScaler. Defaults to 2**32. min_scale (float, optional): Min scale used by DynamicGradScaler. Defaults to 1. growth_factor (float, optional): growth_factor used by DynamicGradScaler. Defaults to 2. backoff_factor (float, optional): backoff_factor used by DynamicGradScaler. Defaults to 0.5. growth_interval (float, optional): growth_interval used by DynamicGradScaler. Defaults to 1000. hysteresis (float, optional): hysteresis used by DynamicGradScaler. Defaults to 2. max_scale (int, optional): max_scale used by DynamicGradScaler. Defaults to 2**32. dp_process_group (Optional[ProcessGroup], optional): data paralle process group. Defaults to None. mp_process_group (Optional[ProcessGroup], optional): model paralle process group. Defaults to None. .. _PatrickStar\: Parallel Training of Pre-trained Models via Chunk-based Memory Management: https://arxiv.org/abs/2108.05818 """ def __init__(self, sharded_model: ShardedModelV2, optimizer: Optimizer, gpu_margin_mem_ratio: float = 0.0, initial_scale: float = 2**32, min_scale: float = 1, growth_factor: float = 2, backoff_factor: float = 0.5, growth_interval: int = 1000, hysteresis: int = 2, max_scale: float = 2**32, dp_process_group: Optional[ProcessGroup] = None, mp_process_group: Optional[ProcessGroup] = None, verbose: bool = False) -> None: assert isinstance(sharded_model, ShardedModelV2), 'model must be wrapped with ShardedModel' super().__init__(optimizer) self.shard_strategy = sharded_model.shard_strategy self.model: ShardedModelV2 = sharded_model self.gpu_margin_mem_ratio: float = float(gpu_margin_mem_ratio) assert 0.0 <= self.gpu_margin_mem_ratio <= 1.0, f'gpu_margin_mem_ratio must >=0.0 and <=1.0' # Only move fp32 shards from CPU to GPU when user allows and inner optimizer is valid # Inner optimizer must support optimizing hybrid (CPU and CUDA) tensors, # and it must set `num_fp32_shards_per_param` correctly self._should_move_fp32_shards_h2d: bool = sharded_model.cpu_offload and self.gpu_margin_mem_ratio > 0.0 and getattr( optimizer, 'num_fp32_shards_per_param', 0) >= 2 self.device = sharded_model._tensor_placement_policy.device or torch.device('cpu') self.optim_state: OptimState = OptimState.UNSCALED self.dp_process_group = dp_process_group or gpc.get_group(ParallelMode.DATA) self.mp_process_group = mp_process_group or gpc.get_group(ParallelMode.MODEL) # Grad scaler self.grad_scaler = DynamicGradScaler(initial_scale=initial_scale, min_scale=min_scale, growth_factor=growth_factor, backoff_factor=backoff_factor, growth_interval=growth_interval, hysteresis=hysteresis, max_scale=max_scale) self._found_overflow: Tensor = torch.IntTensor([0]).to(torch.cuda.current_device()) self._logger = get_dist_logger("ShardedOptimizerV2") self._verbose = verbose # Store fp32 param shards self._register_master_weight() if self.gpu_margin_mem_ratio != 0.0 and not isinstance(sharded_model._tensor_placement_policy, AutoTensorPlacementPolicy): self._logger.warning(f'gpu_margin_mem_ratio is meaningless when tensor_placement_policy is not "auto"', ranks=[0]) if self._verbose: self._logger.debug( f"After init ShardedOptimizerV2 consumes {self.get_memory_usage()[0] / 1e6} MB CUDA Memory!", ranks=[0]) self._use_memory_tracer = self.model.use_memory_tracer @property def loss_scale(self): return self.grad_scaler.scale.item() def get_memory_usage(self) -> Tuple[int, int]: """ Get the memory usage of the optimizer. Including master_params (param fp32), momentum (``self.state[p]['exp_avg']``) variance (``self.state[p]['exp_avg_sq']``) Returns: Tuple[int, int]: cuda/cpu memory usage in Byte. """ cuda_use = 0 cpu_use = 0 def update_mem_use(t): nonlocal cuda_use nonlocal cpu_use t_cuda_use, t_cpu_use = colo_tensor_mem_usage(t) cuda_use += t_cuda_use cpu_use += t_cpu_use for _, p_fp32 in self.master_params.items(): update_mem_use(p_fp32) for group in self.optim.param_groups: for p in group['params']: state = self.optim.state[p] for k, v in state.items(): update_mem_use(v) return cuda_use, cpu_use def zero_grad(self, *args, **kwargs): self._zero_grad() def backward(self, loss: Tensor) -> None: loss = self.loss_scale * loss self.optim_state = OptimState.SCALED self.model.backward(loss) def backward_by_grad(self, tensor: Tensor, grad: Tensor) -> None: self.model.backward_by_grad(tensor, grad) def clip_grad_norm(self, model: nn.Module, max_norm: float): if self.optim_state == OptimState.SCALED: self._unscale_grads() return super().clip_grad_norm(model, max_norm) def step(self, *args, **kwargs): self._prepare_grads() self._maybe_move_fp32_shards() # unscale grads if scaled if self.optim_state == OptimState.SCALED: self._unscale_grads() found_inf = self._check_overflow() self.grad_scaler.update(found_inf) if found_inf: self._logger.warning('found inf during ShardedOptimV2 step') self._zero_grad(recover_data=True) return self._point_param_fp16_to_master_param() if self._verbose: gpu_mem, cpu_mem = self.get_memory_usage() self._logger.debug( f"Before step ShardedOptimizerV2 consumes {gpu_mem / 1e6} MB CUDA Memory, {cpu_mem / 1e6} MB CUDA Memory!", ranks=[0]) ret = self.optim.step(*args, **kwargs) if self._verbose: gpu_mem, cpu_mem = self.get_memory_usage() self._logger.debug( f"After step ShardedOptimizerV2 consumes {gpu_mem / 1e6} MB CUDA Memory, {cpu_mem / 1e6} MB CUDA Memory!", ranks=[0]) self._copy_master_model_to_model_fp16() return ret def _check_overflow(self): # clear previous overflow record self._found_overflow.fill_(self.model.overflow_counter) # all-reduce across dp group dist.all_reduce(self._found_overflow, group=self.dp_process_group) # all-reduce over model parallel group dist.all_reduce(self._found_overflow, group=self.mp_process_group) return self._found_overflow.item() > 0 def _unscale_grads(self): assert self.optim_state == OptimState.SCALED for group in self.optim.param_groups: for p in group['params']: if p.grad is not None: p.grad.data.div_(self.loss_scale) self.optim_state = OptimState.UNSCALED def _zero_grad(self, recover_data: bool = False): """zero grad and maybe recover fp16 params When `reuse_fp16_shard` is enabled, p.colo_attr.sharded_data_tensor stores grad here. We have to recover them from fp32 params. Args: recover_data (bool, optional): Whether to recover fp16 param from fp32 param. Defaults to False. """ # We must set grad to None # Because grad here is sharded # But next backward pass will create a full grad first # Which leads to wrong accumulation self.optim.zero_grad(set_to_none=True) for group in self.optim.param_groups: for p in group['params']: # p.colo_attr.sharded_data_tensor stores grad now # we have to recover fp16 param reuse_fp16_shard = (p.colo_attr.sharded_data_tensor.payload_size == 0) if recover_data and reuse_fp16_shard: self._copy_master_param_to_param_fp16(p) else: # release saved gradient p.colo_attr.saved_grad.set_null() self.model.overflow_counter = 0 # set overflow counter to zero def sync_grad(self): pass def _register_master_weight(self): self.master_params: Dict[Parameter, StatefulTensor] = {} for group in self.optim.param_groups: for p in group['params']: assert hasattr(p, 'colo_attr'), 'The parameter must be wrapped with ShardedParam' shard_flag = not p.colo_attr.sharded_data_tensor.is_sharded and p.colo_attr.is_replicated if shard_flag: # we always shard replicated paramters self.shard_strategy.shard([p.colo_attr.sharded_data_tensor], self.dp_process_group) self.master_params[p] = StatefulTensor(cast_tensor_to_fp32(p.colo_attr.data_payload.to(self.device))) if shard_flag: # In this branch, there's no need to shard param # So we gather here self.shard_strategy.gather([p.colo_attr.sharded_data_tensor], self.dp_process_group) def _maybe_move_fp32_shards(self): if self._should_move_fp32_shards_h2d: self._should_move_fp32_shards_h2d = False available_cuda_margin_mem = self.model.cuda_margin_space * self.gpu_margin_mem_ratio fp32_shards_available_cuda_margin_mem = available_cuda_margin_mem / self.optim.num_fp32_shards_per_param fp32_shards_used_cuda_margin_mem = 0 for group in self.optim.param_groups: for p in group['params']: shard_mem = self.master_params[p].payload.numel() * self.master_params[p].payload.element_size() if fp32_shards_used_cuda_margin_mem + shard_mem < fp32_shards_available_cuda_margin_mem: colo_model_data_tensor_move_inline(self.master_params[p], torch.cuda.current_device()) colo_model_data_tensor_move_inline(p.colo_attr.saved_grad, torch.cuda.current_device()) p.colo_attr.offload_grad = False fp32_shards_used_cuda_margin_mem += shard_mem def _prepare_grads(self): for group in self.optim.param_groups: for p in group['params']: if p.colo_attr.saved_grad.is_null(): continue p.colo_attr.saved_grad.trans_state(TensorState.COMPUTE) # If reuse_fp16_shard, grad fp16 which wasn't be offloaded may be evicted to CPU if not p.colo_attr.offload_grad: colo_model_data_tensor_move_inline(p.colo_attr.saved_grad, torch.cuda.current_device()) # FIXME(ver217): p.data here is an empty tensor on CUDA and has no useful infomation # If we change p.grad directly # it may raise error because of different shape/dtype/device of p.data and p.grad # We just set p.data = p.colo_attr.saved_grad.payload here p.data = p.colo_attr.grad_payload p.grad = p.colo_attr.grad_payload # Set p.data to empty tensor, in case of memory leaking p.colo_attr.set_data_none() def _point_param_fp16_to_master_param(self): # assign master param pointers to p.data. # We will not trigger data copy here. for group in self.optim.param_groups: for p in group['params']: self.master_params[p].trans_state(TensorState.COMPUTE) p.data = self.master_params[p].payload # Now p.data is sharded # So optimizer states are sharded naturally def _copy_master_model_to_model_fp16(self): # Copy master param data (fp32) to payload of colo_attr (fp16) # TODO() improve efficiency by gathering tensors into a chunk and transfering # a chunk. for group in self.optim.param_groups: for p in group['params']: self._copy_master_param_to_param_fp16(p) def _copy_master_param_to_param_fp16(self, p): # flush gradient if p.colo_attr.sharded_data_tensor.payload_size == 0: # here reuse_fp16_shard is True # in order to use copy below, we should give sharded data tensor a payload p.colo_attr.sharded_data_tensor.payload_relay(p.colo_attr.saved_grad) else: p.colo_attr.saved_grad.set_null() p.data = self.master_params[p].payload # we need to allocate new memory for keep_not_shard paramters # in order to use copy, otherwise, the sizes of tensor is not compatible if p.colo_attr.data_payload.numel() != p.data.numel(): p.colo_attr.data_payload_reset( torch.empty(p.data.shape, dtype=p.colo_attr.data_payload.dtype, device=p.colo_attr.data_payload.device)) # TODO() optimize this line CPU (fp32) -> GPU (fp16) p.colo_attr.sharded_data_tensor.payload_copy(p.half().detach()) p.colo_attr.set_data_none() if p.colo_attr.keep_not_shard and p.colo_attr.is_replicated: # We gather full fp16 param here p.colo_attr.sharded_data_tensor.is_sharded = True # since only gradient is sharded, we should set to True self.shard_strategy.gather([p.colo_attr.sharded_data_tensor], self.dp_process_group) self.master_params[p].trans_state(TensorState.HOLD)