[kernel] fixed repeated loading of kernels (#2549)

* [kernel] fixed repeated loading of kernels

* polish code

* polish code

colossalai/kernel/cuda_native/__init__.py

 from .layer_norm import MixedFusedLayerNorm as LayerNorm
 from .multihead_attention import MultiHeadAttention
-from .scaled_softmax import FusedScaleMaskSoftmax
+from .scaled_softmax import FusedScaleMaskSoftmax, ScaledUpperTriangMaskedSoftmax
+
+__all__ = ['LayerNorm', 'MultiHeadAttention', 'FusedScaleMaskSoftmax', 'ScaledUpperTriangMaskedSoftmax']

colossalai/kernel/cuda_native/layer_norm.py

@@ -9,24 +9,31 @@ from torch.cuda.amp import custom_bwd, custom_fwd
 from torch.nn import init
 from torch.nn.parameter import Parameter
 
+from colossalai.kernel.op_builder.layernorm import LayerNormBuilder
+
+try:
+    from colossalai._C import layer_norm
+except ImportError:
+    layer_norm = None
+
 
 class FusedLayerNormAffineFunction(torch.autograd.Function):
 
     @staticmethod
     @custom_fwd(cast_inputs=torch.float32)
     def forward(ctx, input, weight, bias, normalized_shape, eps):
-        try:
-            from colossalai._C import layer_norm
-        except ImportError:
-            from colossalai.kernel.op_builder.layernorm import LayerNormBuilder
-            layer_norm = LayerNormBuilder().load()
-
         ctx.normalized_shape = normalized_shape
         ctx.eps = eps
         input_ = input.contiguous()
         weight_ = weight.contiguous()
         bias_ = bias.contiguous()
+
+        global layer_norm
+        if layer_norm is None:
+
+            layer_norm = LayerNormBuilder().load()
         output, mean, invvar = layer_norm.forward_affine(input_, ctx.normalized_shape, weight_, bias_, ctx.eps)
+        ctx.layernorm_op = layer_norm
         ctx.save_for_backward(input_, weight_, bias_, mean, invvar)
 
         return output
@@ -34,12 +41,6 @@ class FusedLayerNormAffineFunction(torch.autograd.Function):
     @staticmethod
     @custom_bwd
     def backward(ctx, grad_output):
-        try:
-            from colossalai._C import layer_norm
-        except ImportError:
-            from colossalai.kernel.op_builder.layernorm import LayerNormBuilder
-            layer_norm = LayerNormBuilder().load()
-
         input_, weight_, bias_, mean, invvar = ctx.saved_tensors
         grad_input = grad_weight = grad_bias = None
         grad_input, grad_weight, grad_bias \

colossalai/kernel/cuda_native/scaled_softmax.py

-"""This code from NVIDIA Megatron
-   with some changes. """
-
 import enum
 
 import torch
 import torch.nn as nn
 
+from colossalai.kernel.op_builder.scaled_masked_softmax import ScaledMaskedSoftmaxBuilder
+from colossalai.kernel.op_builder.scaled_upper_triangle_masked_softmax import ScaledUpperTrainglemaskedSoftmaxBuilder
+
+try:
+    from colossalai._C import scaled_masked_softmax, scaled_upper_triang_masked_softmax
+except ImportError:
+    scaled_masked_softmax = None
+    scaled_upper_triang_masked_softmax = None
+
 
 class AttnMaskType(enum.Enum):
     padding = 1
@@ -23,7 +29,9 @@ class ScaledUpperTriangMaskedSoftmax(torch.autograd.Function):
 
     @staticmethod
     def forward(ctx, inputs, scale):
-        from colossalai.kernel import scaled_upper_triang_masked_softmax
+        global scaled_upper_triang_masked_softmax
+        if scaled_upper_triang_masked_softmax:
+            scaled_upper_triang_masked_softmax = ScaledUpperTrainglemaskedSoftmaxBuilder().load()
 
         scale_t = torch.tensor([scale])
         softmax_results = scaled_upper_triang_masked_softmax.forward(inputs, scale_t[0])
@@ -33,8 +41,6 @@ class ScaledUpperTriangMaskedSoftmax(torch.autograd.Function):
 
     @staticmethod
     def backward(ctx, output_grads):
-        from colossalai.kernel import scaled_upper_triang_masked_softmax
-
         softmax_results, scale_t = ctx.saved_tensors
         input_grads = scaled_upper_triang_masked_softmax.backward(output_grads, softmax_results, scale_t[0])
 
@@ -52,30 +58,23 @@ class ScaledMaskedSoftmax(torch.autograd.Function):
 
     @staticmethod
     def forward(ctx, inputs, mask, scale):
-        try:
-            from colossalai._C import scaled_masked_softmax
-        except ImportError:
-            from colossalai.kernel.op_builder.scaled_masked_softmax import ScaledMaskedSoftmaxBuilder
-            scaled_masked_softmax = ScaledMaskedSoftmaxBuilder().load()
-
         scale_t = torch.tensor([scale])
 
+        # build and load kernel if not pre-built
+        global scaled_masked_softmax
+        if scaled_masked_softmax is None:
+            scaled_masked_softmax = ScaledMaskedSoftmaxBuilder().load()
+
         softmax_results = scaled_masked_softmax.forward(inputs, mask, scale_t[0])
         ctx.save_for_backward(softmax_results, scale_t)
         return softmax_results
 
     @staticmethod
     def backward(ctx, output_grads):
-        try:
-            from colossalai._C import scaled_masked_softmax
-        except ImportError:
-            from colossalai.kernel.op_builder.scaled_masked_softmax import ScaledMaskedSoftmaxBuilder
-            scaled_masked_softmax = ScaledMaskedSoftmaxBuilder().load()
-
         softmax_results, scale_t = ctx.saved_tensors
 
         input_grads = scaled_masked_softmax.backward(output_grads, softmax_results, scale_t[0])
-        return input_grads, None, None
+        return input_grads, None, None, None
 
 
 class FusedScaleMaskSoftmax(nn.Module):
@@ -113,14 +112,6 @@ class FusedScaleMaskSoftmax(nn.Module):
         self.mask_func = mask_func
         self.softmax_in_fp32 = softmax_in_fp32
         self.scale = scale
-
-        try:
-            from colossalai._C import scaled_masked_softmax
-        except ImportError:
-            from colossalai.kernel.op_builder.scaled_masked_softmax import ScaledMaskedSoftmaxBuilder
-            scaled_masked_softmax = ScaledMaskedSoftmaxBuilder().load()
-        self.scaled_masked_softmax = scaled_masked_softmax
-
         assert (self.scale is None or softmax_in_fp32), "softmax should be in fp32 when scaled"
 
     def forward(self, input, mask):
@@ -186,4 +177,4 @@ class FusedScaleMaskSoftmax(nn.Module):
         return probs
 
     def get_batch_per_block(self, sq, sk, b, np):
-        return self.scaled_masked_softmax.get_batch_per_block(sq, sk, b, np)
+        return scaled_masked_softmax.get_batch_per_block(sq, sk, b, np)

op_builder/builder.py

@@ -6,6 +6,23 @@ from pathlib import Path
 from typing import List
 
 
+def print_rank_0(message):
+    """
+    Print on only one process to avoid spamming.
+    """
+    try:
+        import torch.distributed as dist
+        if not dist.is_initialized():
+            is_main_rank = True
+        else:
+            is_main_rank = dist.get_rank() == 0
+    except ImportError:
+        is_main_rank = True
+
+    if is_main_rank:
+        print(message)
+
+
 class Builder(ABC):
     """
     Builder is the base class to build extensions for PyTorch.
@@ -117,7 +134,7 @@ class Builder(ABC):
         try:
             op_module = self.import_op()
             if verbose:
-                print(f"OP {self.prebuilt_import_path} already exists, skip building.")
+                print_rank_0(f"OP {self.prebuilt_import_path} already exists, skip building.")
         except ImportError:
             # construct the build directory
             import torch
@@ -130,9 +147,11 @@ class Builder(ABC):
             Path(build_directory).mkdir(parents=True, exist_ok=True)
 
             if verbose:
-                print("=========================================================================================")
-                print(f"No pre-built kernel is found, build and load the {self.name} kernel during runtime now")
-                print("=========================================================================================")
+                print_rank_0(
+                    "=========================================================================================")
+                print_rank_0(f"No pre-built kernel is found, build and load the {self.name} kernel during runtime now")
+                print_rank_0(
+                    "=========================================================================================")
 
             # load the kernel
             op_module = load(name=self.name,
@@ -146,7 +165,7 @@ class Builder(ABC):
 
         build_duration = time.time() - start_build
         if verbose:
-            print(f"Time to load {self.name} op: {build_duration} seconds")
+            print_rank_0(f"Time to load {self.name} op: {build_duration} seconds")
 
         return op_module