[gemini] gemini mgr supports "cpu" placement policy

colossalai/gemini/gemini_mgr.py

@@ -1,4 +1,4 @@
-import functools
+import torch
 from .memory_tracer.memstats_collector import MemStatsCollectorV2
 from typing import List, Optional, Tuple
 from time import time
@@ -15,8 +15,6 @@ class GeminiManager:
     """
 
     def __init__(self, placement_policy: str, chunk_manager: ChunkManager) -> None:
-        # TODO: remove assert
-        assert placement_policy == 'cuda', 'placement_policy can only be "cuda" now'
         assert placement_policy in PlacementPolicyFactory.get_polocy_names()
         policy_cls = PlacementPolicyFactory.create(placement_policy)
         self._chunk_manager = chunk_manager
@@ -111,3 +109,7 @@ def cuda_margin_mem(self) -> Optional[float]:
     @property
     def is_cuda_margin_mem_avail(self) -> bool:
         return self._placement_policy.need_mem_stats
+
+    @staticmethod
+    def get_default_device(policy_name: str) -> torch.device:
+        return PlacementPolicyFactory.get_default_device(policy_name)

colossalai/gemini/placement_policy.py

@@ -34,10 +34,11 @@ def __init__(self, chunk_manager: ChunkManager, mem_stats_collector: Optional[Me
 
     def evict_tensors(self, can_evict_chunks: List[Chunk], **kwargs) -> int:
         volume = 0
+        start = time()
         for chunk in can_evict_chunks:
-            self.chunk_manager.move_chunk(chunk, torch.device('cpu'))
+            self.chunk_manager.move_chunk(chunk, torch.device('cpu'), update_ptr=False)
             volume += chunk.mem
-        return volume, 0
+        return volume, time() - start
 
 
 class CUDAPlacementPolicy(PlacementPolicy):
@@ -115,7 +116,7 @@ def evict_tensors(self,
                 if freed_cuda_model_data >= to_free_cuda_model_data:
                     break
                 freed_cuda_model_data += chunk.mem
-                self.chunk_manager.move_chunk(chunk, torch.device('cpu'))
+                self.chunk_manager.move_chunk(chunk, torch.device('cpu'), update_ptr=False)
             if freed_cuda_model_data < to_free_cuda_model_data:
                 raise RuntimeError(
                     f"Adjust layout failed! No enough CUDA memory! Need {to_free_cuda_model_data}, freed {freed_cuda_model_data}"

colossalai/nn/parallel/data_parallel.py

@@ -100,6 +100,8 @@ def __init__(self, module: torch.nn.Module, gemini_manager: GeminiManager) -> No
         self.fp32_params = []
         self.overflow_counter = 0
         self.grads_device: Dict[torch.Tensor, torch.device] = {}
+        self.chunk_manager.create_group('fp16_param', force_data_on_cuda=True)
+        self.chunk_manager.create_group('fp32_param')
         # TODO: get param order and filter unused params
         for p in module.parameters():
             assert p.dtype == torch.half

colossalai/tensor/chunk.py

@@ -36,8 +36,21 @@ class ChunkFullError(Exception):
     pass
 
 
-class Chunk:
+def is_storage_empty(tensor: torch.Tensor) -> bool:
+    return tensor.storage().size() == 0
+
+
+def free_storage(tensor: torch.Tensor) -> None:
+    if not is_storage_empty(tensor):
+        tensor.storage().resize_(0)
+
+
+def alloc_storage(tensor: torch.Tensor) -> None:
+    if is_storage_empty(tensor):
+        tensor.storage().resize_(tensor.numel())
+
 
+class Chunk:
     """
     A chunk is a contiguous memory space which contains multiple tensors.
 
@@ -46,26 +59,37 @@ class Chunk:
         src_rank (int): the process which owns the chunk
         dtype (torch.dtype): the data type of the chunk
         init_device (torch.device): optional, the device where the tensor is initialized. The default value is None, which is the current GPU.
+        force_data_on_cuda (bool): optional, if True, chunk.data is always on cuda. Defaults to False.
     """
 
     def __init__(self,
                  chunk_size: int,
                  src_rank: int,
                  dtype: torch.dtype,
-                 init_device: Optional[torch.device] = None) -> None:
+                 init_device: Optional[torch.device] = None,
+                 force_data_on_cuda: bool = False) -> None:
         self.size = chunk_size
         self.utilized_size = 0
         self.src_rank = src_rank
         self.is_src_rank = gpc.get_local_rank(ParallelMode.DATA) == src_rank
         self.global_src_rank = gpc.get_ranks_in_group(ParallelMode.DATA)[src_rank]
         self.dtype = dtype
-        self.device = init_device or get_current_device()
-        self.data = torch.empty(chunk_size, dtype=dtype, device=self.device)
+        device = init_device or get_current_device()
+        if force_data_on_cuda:
+            self.data = torch.empty(chunk_size, dtype=dtype, device=get_current_device())
+            self._cpu_data = torch.empty(chunk_size, dtype=dtype)
+            if device.type == 'cuda':
+                free_storage(self._cpu_data)
+            else:
+                free_storage(self.data)
+        else:
+            self.data = torch.empty(chunk_size, dtype=dtype, device=device)
+            self._cpu_data = None
 
         # we only keep the chunk in full in the process by which the tensor is owned
         if not self.is_src_rank:
-            self.data.storage().resize_(0)
-        
+            free_storage(self._payload)
+
         # each tensor is associated with a TensorInfo to track meta info
         self.tensors_info: Dict[torch.Tensor, TensorInfo] = {}
         self.mem = self.size * self.data.element_size()
@@ -83,16 +107,16 @@ def append(self, tensor: torch.Tensor) -> None:
         # raise exception when the chunk size is exceeded
         if new_utilized_size > self.size:
             raise ChunkFullError
-        
+
         # set tensor state
         tensor_state = TensorState.FREE
 
         # if the process owns the rank, then copy the tensor to its chunk buffer
         # otherwise set its storage size to 0 to reduce memory consumption
         if self.is_src_rank:
-            self.data[self.utilized_size:new_utilized_size].copy_(tensor.view(-1))
+            self._payload[self.utilized_size:new_utilized_size].copy_(tensor.view(-1))
             tensor_state = TensorState.HOLD
-            tensor.data = self.data[self.utilized_size:new_utilized_size].view(tensor.shape)
+            tensor.data = self._payload[self.utilized_size:new_utilized_size].view(tensor.shape)
         else:
             tensor.storage().resize_(0)
         self.tensors_info[tensor] = TensorInfo(tensor_state, self.utilized_size, new_utilized_size)
@@ -103,12 +127,12 @@ def release(self) -> None:
         Release the memory space on processes which do not own the chunk.
         """
         if not self.is_src_rank:
-            self.data.storage().resize_(0)
+            free_storage(self._payload)
             self._update_tensors_state(TensorState.FREE)
 
     def _update_tensors_ptr(self) -> None:
         for tensor, tensor_info in self.tensors_info.items():
-            tensor.data = self.data[tensor_info.offset:tensor_info.end].view(tensor.shape)
+            tensor.data = self._payload[tensor_info.offset:tensor_info.end].view(tensor.shape)
 
     def _update_tensors_state(self, next_state: TensorState, prev_state: Optional[TensorState] = None):
         for tensor_info in self.tensors_info.values():
@@ -122,24 +146,41 @@ def access(self) -> None:
         # recover the chunk on non-owner processes
         # and broadcast the chunk from the source to all processes
         if not self.is_src_rank:
-            self.data.storage().resize_(self.size)
-        self.data.data = self.data.to(get_current_device())
+            alloc_storage(self._payload)
+        self.move_device(get_current_device(), update_ptr=False)
         dist.broadcast(self.data, self.global_src_rank, group=gpc.get_group(ParallelMode.DATA))
 
         # update tensor meta info
         self._update_tensors_ptr()
         if not self.is_src_rank:
             self._update_tensors_state(TensorState.HOLD, prev_state=TensorState.FREE)
 
-    def move_device(self, device: torch.device) -> None:
+    def move_device(self, device: torch.device, update_ptr: bool = True) -> None:
         """
         Move the chunk to a target device.
 
         Args:
             device (torch.device): the target device for data movement.
         """
-        self.data.data = self.data.to(device)
-        self._update_tensors_ptr()
+        if self._payload.device == device:
+            return
+        if self._cpu_data is None:
+            self.data.data = self.data.to(device)
+        else:
+            if device.type == 'cuda':
+                # cpu -> cuda
+                src = self._cpu_data
+                dest = self.data
+            else:
+                # cuda -> cpu
+                src = self.data
+                dest = self._cpu_data
+            alloc_storage(dest)
+            dest.copy_(src)
+            free_storage(src)
+
+        if update_ptr:
+            self._update_tensors_ptr()
 
     def reduce(self, is_all_reduce: bool = False) -> None:
         """
@@ -148,7 +189,7 @@ def reduce(self, is_all_reduce: bool = False) -> None:
         Args:
             is_all_reduce (bool): optional, whether to all-reduce the chunk. The default is false.
         """
-        self.data.data = self.data.to(get_current_device())
+        self.move_device(get_current_device(), update_ptr=False)
         if is_all_reduce:
             dist.all_reduce(self.data, group=gpc.get_group(ParallelMode.DATA))
         else:
@@ -187,8 +228,8 @@ def copy_tensor_to_chunk_slice(self, tensor: torch.Tensor, data_slice: torch.Ten
             data_slice (torch.Tensor): the tensor to be copied to the chunk
         """
         tensor_info = self.tensors_info[tensor]
-        self.data[tensor_info.offset:tensor_info.end].copy_(data_slice.view(-1))
-        tensor.data = self.data[tensor_info.offset:tensor_info.end].view(tensor.shape)
+        self._payload[tensor_info.offset:tensor_info.end].copy_(data_slice.view(-1))
+        tensor.data = self._payload[tensor_info.offset:tensor_info.end].view(tensor.shape)
 
     @property
     def can_release(self) -> bool:
@@ -225,7 +266,7 @@ def is_empty(self) -> bool:
         """
         Check whether the chunk is empty.
         """
-        return self.data.storage().size() == 0
+        return is_storage_empty(self._payload)
 
     def __repr__(self) -> str:
         return f'Chunk: src rank={self.src_rank} ,size={self.size}, utilization={self.utilized_size/self.size*100:.2f}%, freed={self.is_empty}, tensor states={[info.state.name for info in self.tensors_info.values()]}'
@@ -235,8 +276,8 @@ def has_inf_or_nan(self) -> bool:
         """
         Check if the chunk has inf or nan values.
         """
-        return torch.isinf(self.data[:self.utilized_size]).any().item() or \
-            torch.isnan(self.data[:self.utilized_size]).any().item()
+        return torch.isinf(self._payload[:self.utilized_size]).any().item() or \
+            torch.isnan(self._payload[:self.utilized_size]).any().item()
 
     def copy_(self, dest_chunk: 'Chunk'):
         """
@@ -246,15 +287,15 @@ def copy_(self, dest_chunk: 'Chunk'):
         assert not dest_chunk.is_empty
         assert self.size == dest_chunk.size
         assert self.utilized_size == dest_chunk.utilized_size
-        self.data.copy_(dest_chunk.data)
+        self._payload.copy_(dest_chunk._payload)
         self._update_tensors_ptr()
 
     @property
     def device_type(self) -> str:
         """
         Get the device type of the chunk.
         """
-        return self.data.device.type
+        return self._payload.device.type
 
     def __hash__(self) -> int:
         return hash(id(self))
@@ -265,6 +306,12 @@ def __eq__(self, __o: object) -> bool:
     def get_tensors(self) -> List[torch.Tensor]:
         return list(self.tensors_info.keys())
 
+    @property
+    def _payload(self) -> torch.Tensor:
+        if self._cpu_data is None or is_storage_empty(self._cpu_data):
+            return self.data
+        return self._cpu_data
+
 
 class ChunkManager:
     """
@@ -285,13 +332,25 @@ def __init__(self,
         self.enable_distributed_storage = enable_distributed_storage
         self.device = init_device or get_current_device()
         self.chunk_groups: Dict[str, Deque[Chunk]] = {}
+        self.groups_force_data_on_cuda: Dict[str, bool] = {}
         self.tensor_chunk_map: Dict[torch.Tensor, Chunk] = {}
         self.accessed_chunks: Set[Chunk] = set()
         self.lazy_release_tensors: List[torch.Tensor] = []
         if enable_distributed_storage and chunk_size is None:
             self.rank_load: Dict[str, torch.Tensor] = {}
         self.total_mem: Dict[str, int] = {'cpu': 0, 'cuda': 0}
 
+    def create_group(self, group_name: str, force_data_on_cuda: bool = False) -> None:
+        """Create a chunk group.
+
+        Args:
+            group_name (str): group name
+            force_data_on_cuda (bool, optional): If True, the data of chunks in this group is always on cuda.. Defaults to False.
+        """
+        assert group_name not in self.chunk_groups
+        self.chunk_groups[group_name] = deque()
+        self.groups_force_data_on_cuda[group_name] = force_data_on_cuda
+
     def append_tensor(self, tensor: torch.Tensor, group_name: str) -> None:
         """
         Append a tensor to a chunk.
@@ -304,19 +363,20 @@ def append_tensor(self, tensor: torch.Tensor, group_name: str) -> None:
         if self.chunk_size is not None and tensor.numel() > self.chunk_size:
             raise ValueError(
                 f'Cannot create chunk, got tensor numel ({tensor.numel()}) > chunk size ({self.chunk_size})')
-        if group_name not in self.chunk_groups:
-            self.chunk_groups[group_name] = deque()
-
         try:
             # append the tensor to the last chunk
             self.chunk_groups[group_name][-1].append(tensor)
         except (IndexError, ChunkFullError):
-            # the except statement will be triggered when there is no chunk or 
+            # the except statement will be triggered when there is no chunk or
             # the last chunk in the chunk group is full
             # this will create a new chunk and allocate this chunk to its corresponding process
             chunk_size = self.chunk_size or tensor.numel()
             src_rank = self._get_next_src_rank(group_name)
-            chunk = Chunk(chunk_size, src_rank, tensor.dtype, self.device)
+            chunk = Chunk(chunk_size,
+                          src_rank,
+                          tensor.dtype,
+                          self.device,
+                          force_data_on_cuda=self.groups_force_data_on_cuda[group_name])
 
             if self.enable_distributed_storage and self.chunk_size is None:
                 self.rank_load[group_name][src_rank] += chunk_size
@@ -387,7 +447,7 @@ def release_chunk(self, chunk: Chunk) -> None:
                 # update the memory consumption after releasing
                 self.total_mem[chunk.device_type] -= chunk.mem
 
-    def move_chunk(self, chunk: Chunk, device: torch.device) -> None:
+    def move_chunk(self, chunk: Chunk, device: torch.device, update_ptr: bool = True) -> None:
         """
         Move the chunk to the target device.
 
@@ -399,7 +459,7 @@ def move_chunk(self, chunk: Chunk, device: torch.device) -> None:
             return
         if chunk.can_move_device and not chunk.is_empty:
             self.total_mem[chunk.device_type] -= chunk.mem
-            chunk.move_device(device)
+            chunk.move_device(device, update_ptr=update_ptr)
             self.total_mem[chunk.device_type] += chunk.mem
 
     def trans_tensor_state(self, tensor: torch.Tensor, state: TensorState) -> None:

tests/test_tensor/test_chunk.py

@@ -44,6 +44,7 @@ def run_chunk_zero(use_chunk, use_zero):
     params = [torch.rand(8, 8) for _ in range(3)]
     chunk_size = 128 if use_chunk else None
     chunk_manager = ChunkManager(chunk_size, enable_distributed_storage=use_zero)
+    chunk_manager.create_group('param')
     assert chunk_manager.total_mem['cpu'] == 0
     assert chunk_manager.total_mem['cuda'] == 0
     for p in params: