GPU Memory Query to C API (#12083)

* add support for GPU memory query

* remove lint

include/mxnet/base.h

@@ -222,6 +222,14 @@ struct Context {
    * \return The number of GPUs that are available.
    */
   inline static int32_t GetGPUCount();
+  /*!
+   * \brief get the free and total available memory on a GPU
+   * \param dev the GPU number to query
+   * \param free_mem pointer to the integer holding free GPU memory
+   * \param total_mem pointer to the integer holding total GPU memory
+   * \return No return value
+   */
+  inline static void GetGPUMemoryInformation(int dev, int *free, int *total);
   /*!
    * Create a pinned CPU context.
    * \param dev_id the device id for corresponding GPU.
@@ -326,6 +334,35 @@ inline int32_t Context::GetGPUCount() {
 #endif
 }
 
+inline void Context::GetGPUMemoryInformation(int dev, int *free_mem,
+                                             int *total_mem) {
+#if MXNET_USE_CUDA
+
+  size_t memF, memT;
+  cudaError_t e;
+
+  int curDevice;
+  e = cudaGetDevice(&curDevice);
+  CHECK_EQ(e, cudaSuccess) << " CUDA: " << cudaGetErrorString(e);
+
+  e = cudaSetDevice(dev);
+  CHECK_EQ(e, cudaSuccess) << " CUDA: " << cudaGetErrorString(e);
+
+  e = cudaMemGetInfo(&memF, &memT);
+  CHECK_EQ(e, cudaSuccess) << " CUDA: " << cudaGetErrorString(e);
+
+  e = cudaSetDevice(curDevice);
+  CHECK_EQ(e, cudaSuccess) << " CUDA: " << cudaGetErrorString(e);
+
+  *free_mem = static_cast<int>(memF);
+  *total_mem = static_cast<int>(memT);
+
+#else
+  LOG(FATAL)
+      << "This call is only supported for MXNet built with CUDA support.";
+#endif
+}
+
 inline Context Context::FromString(const std::string& str) {
   Context ret;
   try {

include/mxnet/c_api.h

@@ -437,6 +437,15 @@ MXNET_DLL int MXEngineSetBulkSize(int bulk_size, int* prev_bulk_size);
  */
 MXNET_DLL int MXGetGPUCount(int* out);
 
+/*!
+ * \brief get the free and total available memory on a GPU
+ * \param dev the GPU number to query
+ * \param free_mem pointer to the integer holding free GPU memory
+ * \param total_mem pointer to the integer holding total GPU memory
+ * \return 0 when success, -1 when failure happens
+ */
+MXNET_DLL int MXGetGPUMemoryInformation(int dev, int *free_mem, int *total_mem);
+
 /*!
  * \brief get the MXNet library version as an integer
  * \param pointer to the integer holding the version number

src/c_api/c_api.cc

@@ -122,6 +122,12 @@ int MXGetGPUCount(int* out) {
   API_END();
 }
 
+int MXGetGPUMemoryInformation(int dev, int *free_mem, int *total_mem) {
+  API_BEGIN();
+  Context::GetGPUMemoryInformation(dev, free_mem, total_mem);
+  API_END();
+}
+
 int MXGetVersion(int *out) {
   API_BEGIN();
   *out = static_cast<int>(MXNET_VERSION);