Merge branch 'slym/persist_ln' into 'main'

Persistent layer norm

See merge request ADLR/megatron-lm!351

megatron/arguments.py

@@ -257,6 +257,16 @@ def parse_args(extra_args_provider=None, defaults={},
             'currently distrobuted checkpoint activations only supported for ' \
             'nointerleaved pipeline parallelism'
 
+    TORCH_MAJOR = int(torch.__version__.split('.')[0])
+    TORCH_MINOR = int(torch.__version__.split('.')[1])
+    # Persistent fused layer norm.
+    if TORCH_MAJOR < 1 or (TORCH_MAJOR == 1 and TORCH_MINOR < 11):
+        args.no_persist_layer_norm = True
+        if args.rank == 0:
+            print('Persistent fused layer norm kernel is supported from '
+                  'pytorch v1.11 (nvidia pytorch container paired with v1.11). '
+                  'Defaulting to no_persist_layer_norm=True')
+
     _print_args(args)
     return args
 
@@ -486,6 +496,11 @@ def _add_training_args(parser):
                        help='Disable asynchronous execution of '
                        'tensor-model-parallel all-reduce with weight '
                        'gradient compuation of a column-linear layer.')
+    group.add_argument('--no-persist-layer-norm', action='store_true',
+                       help='Disable using persistent fused layer norm kernel. '
+                       'This kernel supports only a set of hidden sizes. Please '
+                       'check persist_ln_hidden_sizes if your hidden '
+                       'size is supported.')
     return parser
 
 

megatron/model/fused_layer_norm.py

@@ -23,6 +23,8 @@ from torch.nn.parameter import Parameter
 from torch.nn import init
 import importlib
 
+from apex.contrib.layer_norm.layer_norm import FastLayerNormFN
+
 global fused_mix_prec_layer_norm_cuda
 fused_mix_prec_layer_norm_cuda = None
 
@@ -61,13 +63,22 @@ class FusedLayerNormAffineFunction(torch.autograd.Function):
 
 class MixedFusedLayerNorm(torch.nn.Module):
 
-  def __init__(self, normalized_shape, eps=1e-5):
+  def __init__(self, normalized_shape, eps=1e-5, no_persist_layer_norm=True):
         super(MixedFusedLayerNorm, self).__init__()
 
         global fused_mix_prec_layer_norm_cuda
         fused_mix_prec_layer_norm_cuda = importlib.import_module(
           "fused_mix_prec_layer_norm_cuda")
 
+        # List of hiddens sizes supported in the persistent layer norm kernel
+        # If the hidden size is not supported, fall back to the non-persistent
+        # kernel.
+        persist_ln_hidden_sizes = [1024, 1536, 2048, 2304, 3072, 3840, 4096,
+            5120, 6144, 8192, 10240, 12288, 12800, 15360, 16384, 18432, 20480,
+            24576, 25600, 30720, 32768, 40960, 49152, 65536]
+        if normalized_shape not in persist_ln_hidden_sizes:
+            no_persist_layer_norm = True
+
         if isinstance(normalized_shape, numbers.Integral):
             normalized_shape = (normalized_shape,)
         self.normalized_shape = torch.Size(normalized_shape)
@@ -75,6 +86,7 @@ class MixedFusedLayerNorm(torch.nn.Module):
         self.weight = Parameter(torch.Tensor(*normalized_shape))
         self.bias = Parameter(torch.Tensor(*normalized_shape))
         self.reset_parameters()
+        self.no_persist_layer_norm = no_persist_layer_norm
 
 
   def reset_parameters(self):
@@ -85,6 +97,10 @@ class MixedFusedLayerNorm(torch.nn.Module):
 
   def forward(self, input):
 
+    if self.no_persist_layer_norm:
         return FusedLayerNormAffineFunction.apply(
-      input, self.weight, self.bias, self.normalized_shape,self.eps)
+          input, self.weight, self.bias, self.normalized_shape, self.eps)
+    else:
+        return FastLayerNormFN.apply(
+          input, self.weight, self.bias, self.eps)
 

megatron/model/transformer.py

@@ -423,7 +423,8 @@ class ParallelTransformerLayer(MegatronModule):
         # Layernorm on the input data.
         self.input_layernorm = LayerNorm(
             args.hidden_size,
-            eps=args.layernorm_epsilon)
+            eps=args.layernorm_epsilon,
+            no_persist_layer_norm=args.no_persist_layer_norm)
 
         # Self attention.
         self.self_attention = ParallelAttention(
@@ -438,7 +439,8 @@ class ParallelTransformerLayer(MegatronModule):
         # Layernorm on the attention output
         self.post_attention_layernorm = LayerNorm(
             args.hidden_size,
-            eps=args.layernorm_epsilon)
+            eps=args.layernorm_epsilon,
+            no_persist_layer_norm=args.no_persist_layer_norm)
 
         if self.layer_type == LayerType.decoder:
             self.inter_attention = ParallelAttention(
@@ -449,7 +451,8 @@ class ParallelTransformerLayer(MegatronModule):
             # Layernorm on the attention output.
             self.post_inter_attention_layernorm = LayerNorm(
                 args.hidden_size,
-                eps=args.layernorm_epsilon)
+                eps=args.layernorm_epsilon,
+                no_persist_layer_norm=args.no_persist_layer_norm)
 
         # MLP
         self.mlp = ParallelMLP(init_method,
@@ -602,7 +605,8 @@ class ParallelTransformer(MegatronModule):
             # Final layer norm before output.
             self.final_layernorm = LayerNorm(
                 args.hidden_size,
-                eps=args.layernorm_epsilon)
+                eps=args.layernorm_epsilon,
+                no_persist_layer_norm=args.no_persist_layer_norm)
 
     def _get_layer(self, layer_number):
         return self.layers[layer_number]