Cythonize Buffer and MemoryResource classes for performance optimization (#876)

* cythonize _memory.py

* fix

* reduce overhead

* tripped again: Cython enforces type annotations at compile time

* ensure Buffer.handle is None everywhere

* fix test

* nit: avoid extra tuple

* update tests to comply with spec and make Cython 3.1 happy

---------

Co-authored-by: Leo Fang <leof@nvidia.com>

Author: Copilot

…a_core/cuda/core/experimental/_memory.py …_core/cuda/core/experimental/_memory.pyxcuda_core/cuda/core/experimental/_memory.py renamed to cuda_core/cuda/core/experimental/_memory.pyx cuda_core/cuda/core/experimental/_memory.py renamed to cuda_core/cuda/core/experimental/_memory.pyx

@@ -4,13 +4,18 @@
 
 from __future__ import annotations
 
+from libc.stdint cimport uintptr_t
+
+from cuda.core.experimental._utils.cuda_utils cimport (
+    _check_driver_error as raise_if_driver_error,
+)
+
 import abc
-import weakref
 from typing import Tuple, TypeVar, Union
 
 from cuda.core.experimental._dlpack import DLDeviceType, make_py_capsule
 from cuda.core.experimental._stream import Stream, default_stream
-from cuda.core.experimental._utils.cuda_utils import driver, handle_return
+from cuda.core.experimental._utils.cuda_utils import driver
 
 # TODO: define a memory property mixin class and make Buffer and
 # MemoryResource both inherit from it
@@ -23,7 +28,7 @@
 """A type union of :obj:`~driver.CUdeviceptr`, `int` and `None` for hinting :attr:`Buffer.handle`."""
 
 
-class Buffer:
+cdef class Buffer:
     """Represent a handle to allocated memory.
 
     This generic object provides a unified representation for how
@@ -33,34 +38,28 @@ class Buffer:
     Support for data interchange mechanisms are provided by DLPack.
     """
 
-    class _MembersNeededForFinalize:
-        __slots__ = ("ptr", "size", "mr")
-
-        def __init__(self, buffer_obj, ptr, size, mr):
-            self.ptr = ptr
-            self.size = size
-            self.mr = mr
-            weakref.finalize(buffer_obj, self.close)
-
-        def close(self, stream=None):
-            if self.ptr and self.mr is not None:
-                self.mr.deallocate(self.ptr, self.size, stream)
-                self.ptr = 0
-                self.mr = None
+    cdef:
+        uintptr_t _ptr
+        size_t _size
+        object _mr
+        object _ptr_obj
 
-    # TODO: handle ownership? (_mr could be None)
-    __slots__ = ("__weakref__", "_mnff")
-
-    def __new__(self, *args, **kwargs):
+    def __init__(self, *args, **kwargs):
         raise RuntimeError("Buffer objects cannot be instantiated directly. Please use MemoryResource APIs.")
 
     @classmethod
-    def _init(cls, ptr: DevicePointerT, size: int, mr: MemoryResource | None = None):
-        self = super().__new__(cls)
-        self._mnff = Buffer._MembersNeededForFinalize(self, ptr, size, mr)
+    def _init(cls, ptr: DevicePointerT, size_t size, mr: MemoryResource | None = None):
+        cdef Buffer self = Buffer.__new__(cls)
+        self._ptr = <uintptr_t>(int(ptr))
+        self._ptr_obj = ptr
+        self._size = size
+        self._mr = mr
         return self
 
-    def close(self, stream: Stream = None):
+    def __del__(self):
+        self.close()
+
+    cpdef close(self, stream: Stream = None):
         """Deallocate this buffer asynchronously on the given stream.
 
         This buffer is released back to their memory resource
@@ -72,7 +71,11 @@ def close(self, stream: Stream = None):
             The stream object to use for asynchronous deallocation. If None,
             the behavior depends on the underlying memory resource.
         """
-        self._mnff.close(stream)
+        if self._ptr and self._mr is not None:
+            self._mr.deallocate(self._ptr, self._size, stream)
+            self._ptr = 0
+            self._mr = None
+            self._ptr_obj = None
 
     @property
     def handle(self) -> DevicePointerT:
@@ -83,37 +86,37 @@ def handle(self) -> DevicePointerT:
             This handle is a Python object. To get the memory address of the underlying C
             handle, call ``int(Buffer.handle)``.
         """
-        return self._mnff.ptr
+        return self._ptr_obj
 
     @property
     def size(self) -> int:
         """Return the memory size of this buffer."""
-        return self._mnff.size
+        return self._size
 
     @property
     def memory_resource(self) -> MemoryResource:
         """Return the memory resource associated with this buffer."""
-        return self._mnff.mr
+        return self._mr
 
     @property
     def is_device_accessible(self) -> bool:
         """Return True if this buffer can be accessed by the GPU, otherwise False."""
-        if self._mnff.mr is not None:
-            return self._mnff.mr.is_device_accessible
+        if self._mr is not None:
+            return self._mr.is_device_accessible
         raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
 
     @property
     def is_host_accessible(self) -> bool:
         """Return True if this buffer can be accessed by the CPU, otherwise False."""
-        if self._mnff.mr is not None:
-            return self._mnff.mr.is_host_accessible
+        if self._mr is not None:
+            return self._mr.is_host_accessible
         raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
 
     @property
     def device_id(self) -> int:
         """Return the device ordinal of this buffer."""
-        if self._mnff.mr is not None:
-            return self._mnff.mr.device_id
+        if self._mr is not None:
+            return self._mr.device_id
         raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
 
     def copy_to(self, dst: Buffer = None, *, stream: Stream) -> Buffer:
@@ -134,15 +137,21 @@ def copy_to(self, dst: Buffer = None, *, stream: Stream) -> Buffer:
         """
         if stream is None:
             raise ValueError("stream must be provided")
+        
+        cdef size_t src_size = self._size
+        
         if dst is None:
-            if self._mnff.mr is None:
+            if self._mr is None:
                 raise ValueError("a destination buffer must be provided (this buffer does not have a memory_resource)")
-            dst = self._mnff.mr.allocate(self._mnff.size, stream)
-        if dst._mnff.size != self._mnff.size:
+            dst = self._mr.allocate(src_size, stream)
+        
+        cdef size_t dst_size = dst._size
+        if dst_size != src_size:
             raise ValueError(
-                f"buffer sizes mismatch between src and dst (sizes are: src={self._mnff.size}, dst={dst._mnff.size})"
+                f"buffer sizes mismatch between src and dst (sizes are: src={src_size}, dst={dst_size})"
             )
-        handle_return(driver.cuMemcpyAsync(dst._mnff.ptr, self._mnff.ptr, self._mnff.size, stream.handle))
+        err, = driver.cuMemcpyAsync(dst._ptr, self._ptr, src_size, stream.handle)
+        raise_if_driver_error(err)
         return dst
 
     def copy_from(self, src: Buffer, *, stream: Stream):
@@ -159,11 +168,16 @@ def copy_from(self, src: Buffer, *, stream: Stream):
         """
         if stream is None:
             raise ValueError("stream must be provided")
-        if src._mnff.size != self._mnff.size:
+            
+        cdef size_t dst_size = self._size
+        cdef size_t src_size = src._size
+        
+        if src_size != dst_size:
             raise ValueError(
-                f"buffer sizes mismatch between src and dst (sizes are: src={src._mnff.size}, dst={self._mnff.size})"
+                f"buffer sizes mismatch between src and dst (sizes are: src={src_size}, dst={dst_size})"
             )
-        handle_return(driver.cuMemcpyAsync(self._mnff.ptr, src._mnff.ptr, self._mnff.size, stream.handle))
+        err, = driver.cuMemcpyAsync(self._ptr, src._ptr, dst_size, stream.handle)
+        raise_if_driver_error(err)
 
     def __dlpack__(
         self,
@@ -189,13 +203,14 @@ def __dlpack__(
         return capsule
 
     def __dlpack_device__(self) -> Tuple[int, int]:
-        d_h = (bool(self.is_device_accessible), bool(self.is_host_accessible))
-        if d_h == (True, False):
+        cdef bint d = self.is_device_accessible
+        cdef bint h = self.is_host_accessible
+        if d and (not h):
             return (DLDeviceType.kDLCUDA, self.device_id)
-        if d_h == (True, True):
+        if d and h:
             # TODO: this can also be kDLCUDAManaged, we need more fine-grained checks
             return (DLDeviceType.kDLCUDAHost, 0)
-        if d_h == (False, True):
+        if (not d) and h:
             return (DLDeviceType.kDLCPU, 0)
         raise BufferError("buffer is neither device-accessible nor host-accessible")
 
@@ -211,7 +226,7 @@ def __release_buffer__(self, buffer: memoryview, /):
         raise NotImplementedError("WIP: Buffer.__release_buffer__ hasn't been implemented yet.")
 
     @staticmethod
-    def from_handle(ptr: DevicePointerT, size: int, mr: MemoryResource | None = None) -> Buffer:
+    def from_handle(ptr: DevicePointerT, size_t size, mr: MemoryResource | None = None) -> Buffer:
         """Create a new :class:`Buffer` object from a pointer.
 
         Parameters
@@ -247,7 +262,7 @@ def __init__(self, *args, **kwargs):
         ...
 
     @abc.abstractmethod
-    def allocate(self, size: int, stream: Stream = None) -> Buffer:
+    def allocate(self, size_t size, stream: Stream = None) -> Buffer:
         """Allocate a buffer of the requested size.
 
         Parameters
@@ -268,7 +283,7 @@ def allocate(self, size: int, stream: Stream = None) -> Buffer:
         ...
 
     @abc.abstractmethod
-    def deallocate(self, ptr: DevicePointerT, size: int, stream: Stream = None):
+    def deallocate(self, ptr: DevicePointerT, size_t size, stream: Stream = None):
         """Deallocate a buffer previously allocated by this resource.
 
         Parameters
@@ -323,27 +338,28 @@ class DeviceMemoryResource(MemoryResource):
     __slots__ = ("_dev_id",)
 
     def __init__(self, device_id: int):
-        self._handle = handle_return(driver.cuDeviceGetMemPool(device_id))
+        err, self._handle = driver.cuDeviceGetMemPool(device_id)
+        raise_if_driver_error(err)
         self._dev_id = device_id
 
         # Set a higher release threshold to improve performance when there are no active allocations.
         # By default, the release threshold is 0, which means memory is immediately released back
         # to the OS when there are no active suballocations, causing performance issues.
         # Check current release threshold
-        current_threshold = handle_return(
-            driver.cuMemPoolGetAttribute(self._handle, driver.CUmemPool_attribute.CU_MEMPOOL_ATTR_RELEASE_THRESHOLD)
+        err, current_threshold = driver.cuMemPoolGetAttribute(
+            self._handle, driver.CUmemPool_attribute.CU_MEMPOOL_ATTR_RELEASE_THRESHOLD
         )
+        raise_if_driver_error(err)
         # If threshold is 0 (default), set it to maximum to retain memory in the pool
         if int(current_threshold) == 0:
-            handle_return(
-                driver.cuMemPoolSetAttribute(
-                    self._handle,
-                    driver.CUmemPool_attribute.CU_MEMPOOL_ATTR_RELEASE_THRESHOLD,
-                    driver.cuuint64_t(0xFFFFFFFFFFFFFFFF),
-                )
+            err, = driver.cuMemPoolSetAttribute(
+                self._handle,
+                driver.CUmemPool_attribute.CU_MEMPOOL_ATTR_RELEASE_THRESHOLD,
+                driver.cuuint64_t(0xFFFFFFFFFFFFFFFF),
             )
+            raise_if_driver_error(err)
 
-    def allocate(self, size: int, stream: Stream = None) -> Buffer:
+    def allocate(self, size_t size, stream: Stream = None) -> Buffer:
         """Allocate a buffer of the requested size.
 
         Parameters
@@ -362,10 +378,11 @@ def allocate(self, size: int, stream: Stream = None) -> Buffer:
         """
         if stream is None:
             stream = default_stream()
-        ptr = handle_return(driver.cuMemAllocFromPoolAsync(size, self._handle, stream.handle))
+        err, ptr = driver.cuMemAllocFromPoolAsync(size, self._handle, stream.handle)
+        raise_if_driver_error(err)
         return Buffer._init(ptr, size, self)
 
-    def deallocate(self, ptr: DevicePointerT, size: int, stream: Stream = None):
+    def deallocate(self, ptr: DevicePointerT, size_t size, stream: Stream = None):
         """Deallocate a buffer previously allocated by this resource.
 
         Parameters
@@ -380,7 +397,8 @@ def deallocate(self, ptr: DevicePointerT, size: int, stream: Stream = None):
         """
         if stream is None:
             stream = default_stream()
-        handle_return(driver.cuMemFreeAsync(ptr, stream.handle))
+        err, = driver.cuMemFreeAsync(ptr, stream.handle)
+        raise_if_driver_error(err)
 
     @property
     def is_device_accessible(self) -> bool:
@@ -407,7 +425,7 @@ def __init__(self):
         # TODO: support flags from cuMemHostAlloc?
         self._handle = None
 
-    def allocate(self, size: int, stream: Stream = None) -> Buffer:
+    def allocate(self, size_t size, stream: Stream = None) -> Buffer:
         """Allocate a buffer of the requested size.
 
         Parameters
@@ -422,10 +440,11 @@ def allocate(self, size: int, stream: Stream = None) -> Buffer:
         Buffer
             The allocated buffer object, which is accessible on both host and device.
         """
-        ptr = handle_return(driver.cuMemAllocHost(size))
+        err, ptr = driver.cuMemAllocHost(size)
+        raise_if_driver_error(err)
         return Buffer._init(ptr, size, self)
 
-    def deallocate(self, ptr: DevicePointerT, size: int, stream: Stream = None):
+    def deallocate(self, ptr: DevicePointerT, size_t size, stream: Stream = None):
         """Deallocate a buffer previously allocated by this resource.
 
         Parameters
@@ -440,7 +459,8 @@ def deallocate(self, ptr: DevicePointerT, size: int, stream: Stream = None):
         """
         if stream:
             stream.sync()
-        handle_return(driver.cuMemFreeHost(ptr))
+        err, = driver.cuMemFreeHost(ptr)
+        raise_if_driver_error(err)
 
     @property
     def is_device_accessible(self) -> bool:
@@ -466,14 +486,16 @@ def __init__(self, device_id):
         self._dev_id = device_id
 
     def allocate(self, size, stream=None) -> Buffer:
-        ptr = handle_return(driver.cuMemAlloc(size))
+        err, ptr = driver.cuMemAlloc(size)
+        raise_if_driver_error(err)
         return Buffer._init(ptr, size, self)
 
     def deallocate(self, ptr, size, stream=None):
         if stream is None:
             stream = default_stream()
         stream.sync()
-        handle_return(driver.cuMemFree(ptr))
+        err, = driver.cuMemFree(ptr)
+        raise_if_driver_error(err)
 
     @property
     def is_device_accessible(self) -> bool:

cuda_core/docs/source/release/0.X.Y-notes.rst

@@ -19,6 +19,7 @@ Breaking Changes
 ----------------
 
 - **LaunchConfig grid parameter interpretation**: When :attr:`LaunchConfig.cluster` is specified, the :attr:`LaunchConfig.grid` parameter now correctly represents the number of clusters instead of blocks. Previously, the grid parameter was incorrectly interpreted as blocks, causing a mismatch with the expected C++ behavior. This change ensures that ``LaunchConfig(grid=4, cluster=2, block=32)`` correctly produces 4 clusters × 2 blocks/cluster = 8 total blocks, matching the C++ equivalent ``cudax::make_hierarchy(cudax::grid_dims(4), cudax::cluster_dims(2), cudax::block_dims(32))``.
+- When :class:`Buffer` is closed, :attr:`Buffer.handle` is now set to `None`. It was previously set to ``0`` by accident.
 
 
 New features
@@ -40,4 +41,5 @@ Fixes and enhancements
 - Improved :class:`DeviceMemoryResource` allocation performance when there are no active allocations by setting a higher release threshold (addresses issue #771).
 - Improved :class:`StridedMemoryView` creation time performance by optimizing shape and strides tuple creation using Python/C API (addresses issue #449).
 - Fix :class:`LaunchConfig` grid unit conversion when cluster is set (addresses issue #867).
-- Fixed a bug in :class:`GraphBuilder.add_child` where dependencies extracted from capturing stream were passed inconsistently with num_dependencies parameter (addresses issue #843).
+- Fixed a bug in :class:`GraphBuilder.add_child` where dependencies extracted from capturing stream were passed inconsistently with num_dependencies parameter (addresses issue #843).
+- Make :class:`Buffer` creation more performant.

cuda_core/examples/memory_ops.py

@@ -129,8 +129,8 @@
 cp.cuda.Stream.null.use()  # reset CuPy's current stream to the null stream
 
 # Verify buffers are properly closed
-assert device_buffer.handle == 0, "Device buffer should be closed"
-assert pinned_buffer.handle == 0, "Pinned buffer should be closed"
-assert new_device_buffer.handle == 0, "New device buffer should be closed"
+assert device_buffer.handle is None, "Device buffer should be closed"
+assert pinned_buffer.handle is None, "Pinned buffer should be closed"
+assert new_device_buffer.handle is None, "New device buffer should be closed"
 
 print("Memory management example completed!")