Add RAII managed CudaGraph class

mlx/backend/cuda/conv.cpp

@@ -193,10 +193,7 @@ bool execute_plan(
   cudnnSetStream(handle, encoder.stream());
 
 #if CUDNN_VERSION >= 90500 && MLX_USE_CUDNN_NATIVE_CUDA_GRAPH_API
-  cudaGraph_t graph;
-  cudaGraphCreate(&graph, 0);
-  std::unique_ptr<cudaGraph_t, void (*)(cudaGraph_t*)> graph_freer(
-      &graph, [](cudaGraph_t* p) { cudaGraphDestroy(*p); });
+  CudaGraph graph(encoder.device());
   if (cudnnBackendPopulateCudaGraph(
           handle, plan.get_raw_desc(), variantPack.get_raw_desc(), graph) !=
       CUDNN_STATUS_SUCCESS) {

mlx/backend/cuda/device.cpp

@@ -91,9 +91,7 @@ CommandEncoder::CaptureContext::CaptureContext(CommandEncoder& enc) : enc(enc) {
 }
 
 CommandEncoder::CaptureContext::~CaptureContext() {
-  CHECK_CUDA_ERROR(cudaStreamEndCapture(enc.stream(), &graph));
-  std::unique_ptr<cudaGraph_t, void (*)(cudaGraph_t*)> graph_freer(
-      &graph, [](cudaGraph_t* p) { CHECK_CUDA_ERROR(cudaGraphDestroy(*p)); });
+  graph.end_capture(enc.stream());
   if (discard) {
     return;
   }
@@ -185,9 +183,10 @@ void CommandEncoder::insert_graph_dependencies(std::vector<GraphNode> nodes) {
 }
 
 CommandEncoder::CommandEncoder(Device& d)
-    : device_(d), stream_(d), graph_cache_(cuda_graph_cache_size()) {
-  CHECK_CUDA_ERROR(cudaGraphCreate(&graph_, 0));
-}
+    : device_(d),
+      stream_(d),
+      graph_(d),
+      graph_cache_(cuda_graph_cache_size()) {}
 
 void CommandEncoder::add_completed_handler(std::function<void()> task) {
   worker_.add_task(std::move(task));
@@ -311,8 +310,7 @@ void CommandEncoder::commit() {
     to_nodes_.clear();
     graph_key_.clear();
     node_map_.clear();
-    CHECK_CUDA_ERROR(cudaGraphDestroy(graph_));
-    CHECK_CUDA_ERROR(cudaGraphCreate(&graph_, 0));
+    graph_ = CudaGraph(device_);
   }
 
   // Put completion handlers in a batch.

mlx/backend/cuda/device.h

@@ -21,7 +21,7 @@ class CommandEncoder {
   struct CaptureContext {
     CaptureContext(CommandEncoder& enc);
     ~CaptureContext();
-    cudaGraph_t graph;
+    CudaGraph graph;
     CommandEncoder& enc;
     bool discard{false};
   };
@@ -115,7 +115,7 @@ class CommandEncoder {
 
   Device& device_;
   CudaStream stream_;
-  cudaGraph_t graph_;
+  CudaGraph graph_;
   Worker worker_;
   char node_count_{0};
   char graph_node_count_{0};

mlx/backend/cuda/utils.cpp

@@ -8,36 +8,6 @@
 
 namespace mlx::core {
 
-CudaStream::CudaStream(cu::Device& device) {
-  device.make_current();
-  CHECK_CUDA_ERROR(cudaStreamCreateWithFlags(&stream_, cudaStreamNonBlocking));
-}
-
-CudaStream::~CudaStream() {
-  CHECK_CUDA_ERROR(cudaStreamDestroy(stream_));
-}
-
-CudaGraphExec::CudaGraphExec(cudaGraphExec_t handle) : handle_(handle) {}
-
-CudaGraphExec::CudaGraphExec(CudaGraphExec&& other) : handle_(other.handle_) {
-  other.handle_ = nullptr;
-};
-
-CudaGraphExec::~CudaGraphExec() {
-  reset();
-}
-
-void CudaGraphExec::instantiate(cudaGraph_t graph) {
-  CHECK_CUDA_ERROR(cudaGraphInstantiate(&handle_, graph, nullptr, nullptr, 0));
-}
-
-void CudaGraphExec::reset() {
-  if (handle_ != nullptr) {
-    CHECK_CUDA_ERROR(cudaGraphExecDestroy(handle_));
-    handle_ = nullptr;
-  }
-}
-
 void check_cublas_error(const char* name, cublasStatus_t err) {
   if (err != CUBLAS_STATUS_SUCCESS) {
     // TODO: Use cublasGetStatusString when it is widely available.
@@ -96,4 +66,24 @@ const char* dtype_to_cuda_type(const Dtype& dtype) {
   }
 }
 
+CudaGraph::CudaGraph(cu::Device& device) {
+  device.make_current();
+  CHECK_CUDA_ERROR(cudaGraphCreate(&handle_, 0));
+}
+
+void CudaGraph::end_capture(cudaStream_t stream) {
+  assert(handle_ == nullptr);
+  CHECK_CUDA_ERROR(cudaStreamEndCapture(stream, &handle_));
+}
+
+void CudaGraphExec::instantiate(cudaGraph_t graph) {
+  assert(handle_ == nullptr);
+  CHECK_CUDA_ERROR(cudaGraphInstantiate(&handle_, graph, nullptr, nullptr, 0));
+}
+
+CudaStream::CudaStream(cu::Device& device) {
+  device.make_current();
+  CHECK_CUDA_ERROR(cudaStreamCreateWithFlags(&handle_, cudaStreamNonBlocking));
+}
+
 } // namespace mlx::core

mlx/backend/cuda/utils.h

@@ -16,44 +16,6 @@ class Device;
 
 struct Dtype;
 
-// Cuda stream managed with RAII.
-class CudaStream {
- public:
-  explicit CudaStream(cu::Device& device);
-  ~CudaStream();
-
-  CudaStream(const CudaStream&) = delete;
-  CudaStream& operator=(const CudaStream&) = delete;
-
-  operator cudaStream_t() const {
-    return stream_;
-  }
-
- private:
-  cudaStream_t stream_;
-};
-
-// Move-able RAII handle of cudaGraphExec_t.
-class CudaGraphExec {
- public:
-  CudaGraphExec(cudaGraphExec_t handle = nullptr);
-  CudaGraphExec(CudaGraphExec&& other);
-  ~CudaGraphExec();
-
-  CudaGraphExec(const CudaGraphExec&) = delete;
-  CudaGraphExec& operator=(const CudaGraphExec&) = delete;
-
-  void instantiate(cudaGraph_t graph);
-  void reset();
-
-  operator cudaGraphExec_t() const {
-    return handle_;
-  }
-
- private:
-  cudaGraphExec_t handle_;
-};
-
 // Throw exception if the cuda API does not succeed.
 void check_cublas_error(const char* name, cublasStatus_t err);
 void check_cuda_error(const char* name, cudaError_t err);
@@ -66,4 +28,62 @@ void check_cuda_error(const char* name, CUresult err);
 // Convert Dtype to CUDA C++ types.
 const char* dtype_to_cuda_type(const Dtype& dtype);
 
+// Base class for RAII managed CUDA resources.
+template <typename Handle, cudaError_t (*Destroy)(Handle)>
+class CudaHandle {
+ public:
+  CudaHandle(Handle handle = nullptr) : handle_(handle) {}
+
+  CudaHandle(CudaHandle&& other) : handle_(other.handle_) {
+    assert(this != &other);
+    other.handle_ = nullptr;
+  }
+
+  ~CudaHandle() {
+    reset();
+  }
+
+  CudaHandle(const CudaHandle&) = delete;
+  CudaHandle& operator=(const CudaHandle&) = delete;
+
+  CudaHandle& operator=(CudaHandle&& other) {
+    assert(this != &other);
+    reset();
+    std::swap(handle_, other.handle_);
+    return *this;
+  }
+
+  void reset() {
+    if (handle_ != nullptr) {
+      CHECK_CUDA_ERROR(Destroy(handle_));
+      handle_ = nullptr;
+    }
+  }
+
+  operator Handle() const {
+    return handle_;
+  }
+
+ protected:
+  Handle handle_;
+};
+
+// Wrappers of CUDA resources.
+class CudaGraph : public CudaHandle<cudaGraph_t, cudaGraphDestroy> {
+ public:
+  using CudaHandle::CudaHandle;
+  explicit CudaGraph(cu::Device& device);
+  void end_capture(cudaStream_t stream);
+};
+
+class CudaGraphExec : public CudaHandle<cudaGraphExec_t, cudaGraphExecDestroy> {
+ public:
+  void instantiate(cudaGraph_t graph);
+};
+
+class CudaStream : public CudaHandle<cudaStream_t, cudaStreamDestroy> {
+ public:
+  explicit CudaStream(cu::Device& device);
+};
+
 } // namespace mlx::core