[ET-VK] Enforce GPU buffer limit when partitioning (#6856)

Pull Request resolved: #6829

## Context

In Vulkan, there is a limit on the number of elements a GPU buffer can have. If a GPU buffer exceeds this limit, then the API will either produce an error or undefined behaviour will ensue.

## Changes

Along with `texture_limits`, introduce a configurable `buffer_limit` entry in the partitioner configuration.
ghstack-source-id: 253568943

Differential Revision: [D65899828](https://our.internmc.facebook.com/intern/diff/D65899828/)

Co-authored-by: Stephen Jia <[email protected]>

Author: pytorchbot

backends/vulkan/partitioner/vulkan_partitioner.py

@@ -51,11 +51,15 @@
 
 class VulkanSupportedOperators(OperatorSupportBase):
     def __init__(
-        self, texture_limits: utils.ImageExtents, require_dynamic_shape: bool = False
+        self,
+        texture_limits: utils.ImageExtents,
+        buffer_limit: int,
+        require_dynamic_shape: bool = False,
     ) -> None:
         super().__init__()
-        self.require_dynamic_shapes = require_dynamic_shape
         self.texture_limits: utils.ImageExtents = texture_limits
+        self.buffer_limit = buffer_limit
+        self.require_dynamic_shapes = require_dynamic_shape
 
     def op_node_is_compatible(
         self, node: torch.fx.Node, features: Optional[OpFeatures] = None
@@ -83,6 +87,7 @@ def op_node_is_compatible(
             node, self.texture_limits
         )
 
+        can_use_buffers = utils.within_buffer_limit(node, self.buffer_limit)
         for i, arg in enumerate(node.args):
             if (
                 isinstance(arg, torch.fx.Node)
@@ -95,10 +100,19 @@ def op_node_is_compatible(
                 valid_texture_layouts = valid_texture_layouts.intersection(
                     arg_texture_layouts
                 )
+                can_use_buffers = can_use_buffers and utils.within_buffer_limit(
+                    arg, self.buffer_limit
+                )
 
         # If there are no valid texture memory layouts, then buffer storage must be
         # supported by the operator implementation.
         if len(valid_texture_layouts) == 0:
+            if not can_use_buffers:
+                return (
+                    False,
+                    f"op requires buffers that exceed the buffer limit ({self.buffer_limit})",
+                )
+
             compatible = VkStorageType.BUFFER in features.supported_storage_types()
             reason = "op is compatible"
             if not compatible:
@@ -309,10 +323,12 @@ def partition(self, exported_program: ExportedProgram) -> PartitionResult:
         texture_limits: utils.ImageExtents = self.options.get(
             "texture_limits", utils.DEFAULT_TEXTURE_LIMITS
         )
+        buffer_limit: int = self.options.get("buffer_limit", utils.DEFAULT_BUFFER_LIMIT)
         capability_partitioner = CapabilityBasedPartitioner(
             exported_program.graph_module,
             VulkanSupportedOperators(
                 texture_limits,
+                buffer_limit,
                 require_dynamic_shape=self.options.get("require_dynamic_shapes", False),
             ),
             allows_single_node_partition=True,

backends/vulkan/utils.py

@@ -87,6 +87,7 @@ def is_tensor_node(node: torch.fx.Node) -> bool:
 ImageExtents = Tuple[int, int, int]
 
 DEFAULT_TEXTURE_LIMITS = (16384, 16384, 2048)
+DEFAULT_BUFFER_LIMIT = 128 * (1024 * 1024)
 
 
 class PackedDim(IntEnum):
@@ -113,6 +114,22 @@ class PackedDim(IntEnum):
 }
 
 
+def within_buffer_limit(node: torch.fx.Node, buffer_limit: int) -> int:
+    """
+    Checks whether the tensors produced by the given node can fit within the device's
+    GPU buffer limit, which represents the maximum number of elements that can be stored
+    in a GPU buffer.
+    """
+    assert is_tensor_node(node)
+
+    if isinstance(node.meta["val"], FakeTensor):
+        return node.meta["val"].numel() < buffer_limit
+    elif isinstance(node.meta["val"], list) or isinstance(node.meta["val"], tuple):
+        return all(x.numel() < buffer_limit for x in node.meta["val"])
+    else:
+        raise RuntimeError(f"Cannot get numel for val of type {type(node.meta['val'])}")
+
+
 def required_image_extents(sizes: torch.Size, layout: VkMemoryLayout) -> ImageExtents:
     """
     Calculate the image extents that will be used to represent a tensor with the given sizes