Move sharding optimization flag to global_settings (#2665)

Summary:
Pull Request resolved: #2665

As per title move the configuration flag to separate module for better abstraction and simpler rollout

Reviewed By: iamzainhuda

Differential Revision: D67777011

fbshipit-source-id: 8a659bee7b81d3181c4014fdf2678c69b306b8c1

Author: Boris Sarana

torchrec/distributed/embedding_types.py

@@ -9,7 +9,6 @@
 
 import abc
 import copy
-import os
 from dataclasses import dataclass
 from enum import Enum, unique
 from typing import Any, Dict, Generic, Iterator, List, Optional, Tuple, TypeVar, Union
@@ -21,6 +20,9 @@
 from torch.distributed._tensor.placement_types import Placement
 from torch.nn.modules.module import _addindent
 from torch.nn.parallel import DistributedDataParallel
+from torchrec.distributed.global_settings import (
+    construct_sharded_tensor_from_metadata_enabled,
+)
 from torchrec.distributed.types import (
     get_tensor_size_bytes,
     ModuleSharder,
@@ -346,8 +348,7 @@ def __init__(
 
         # option to construct ShardedTensor from metadata avoiding expensive all-gather
         self._construct_sharded_tensor_from_metadata: bool = (
-            os.environ.get("TORCHREC_CONSTRUCT_SHARDED_TENSOR_FROM_METADATA", "0")
-            == "1"
+            construct_sharded_tensor_from_metadata_enabled()
         )
 
     def prefetch(

torchrec/distributed/global_settings.py

@@ -7,8 +7,14 @@
 
 # pyre-strict
 
+import os
+
 PROPOGATE_DEVICE: bool = False
 
+TORCHREC_CONSTRUCT_SHARDED_TENSOR_FROM_METADATA_ENV = (
+    "TORCHREC_CONSTRUCT_SHARDED_TENSOR_FROM_METADATA"
+)
+
 
 def set_propogate_device(val: bool) -> None:
     global PROPOGATE_DEVICE
@@ -18,3 +24,9 @@ def set_propogate_device(val: bool) -> None:
 def get_propogate_device() -> bool:
     global PROPOGATE_DEVICE
     return PROPOGATE_DEVICE
+
+
+def construct_sharded_tensor_from_metadata_enabled() -> bool:
+    return (
+        os.environ.get(TORCHREC_CONSTRUCT_SHARDED_TENSOR_FROM_METADATA_ENV, "0") == "1"
+    )