fix nits from deletion of Float8DynamicLinear

Summary:

Addressing a couple of nits that slipped in
#304

* more defaults to dynamic
* undo repr change
* fix comment

Test Plan:

```
./test/test_everything.sh
```

Reviewers:

Subscribers:

Tasks:

Tags:

[ghstack-poisoned]

Author: vkuzo

float8_experimental/float8_linear.py

@@ -165,9 +165,9 @@ def __init__(self, *args, **kwargs):
         # Amax scales should always be kept as float32.
         self.always_float32_buffers = set()
         emulate = kwargs.pop("emulate", False)
-        scaling_type_x = kwargs.pop("scaling_type_x", TensorScalingType.DELAYED)
-        scaling_type_w = kwargs.pop("scaling_type_w", TensorScalingType.DELAYED)
-        scaling_type_dL_dY = kwargs.pop("scaling_type_dL_dY", TensorScalingType.DELAYED)
+        scaling_type_x = kwargs.pop("scaling_type_x", TensorScalingType.DYNAMIC)
+        scaling_type_w = kwargs.pop("scaling_type_w", TensorScalingType.DYNAMIC)
+        scaling_type_dL_dY = kwargs.pop("scaling_type_dL_dY", TensorScalingType.DYNAMIC)
         super().__init__(*args, **kwargs)
 
         # Defines the scaling behavior of x, w, dL_dY
@@ -402,8 +402,8 @@ def forward(self, input: torch.Tensor) -> torch.Tensor:
 
     def scaling_repr(self):
         # add scaling settings without using too many characters
-        # example: "x_del_w_del_dldy_dyn"
-        return f"x_{self.scaling_type_x.short_str()}_w_{self.scaling_type_w.short_str()}_dldy_{self.scaling_type_dL_dY.short_str()}"
+        # example: "x:del,w:del,dldy:dyn"
+        return f"x:{self.scaling_type_x.short_str()},w:{self.scaling_type_w.short_str()},dldy:{self.scaling_type_dL_dY.short_str()}"
 
     def extra_repr(self):
         s = f'{super().extra_repr()}, scaling="{self.scaling_repr()}"'
@@ -414,9 +414,9 @@ def from_float(
         cls,
         mod,
         emulate: bool = False,
-        scaling_type_x=TensorScalingType.DELAYED,
-        scaling_type_w=TensorScalingType.DELAYED,
-        scaling_type_dL_dY=TensorScalingType.DELAYED,
+        scaling_type_x=TensorScalingType.DYNAMIC,
+        scaling_type_w=TensorScalingType.DYNAMIC,
+        scaling_type_dL_dY=TensorScalingType.DYNAMIC,
     ):
         """
         Create an nn.Linear with fp8 compute from a regular nn.Linear

test/test_dtensor.py

@@ -171,8 +171,7 @@ def _test_fp8_mlp_tensor_parallelism_base(
     mesh: DeviceMesh, size=16, compile: bool = False
 ):
     device = mesh.device_type
-    # For now, just use Float8Linear with dynamic scaling, which is the
-    # same behavior as Float8Linear.
+    # For now, only supports dynamic scaling of `x` and `dL_dY`.
     # TODO(future): add support for float8 all-gather with delayed scaling
     # for activations and gradients.
     extra_kwargs = {