compute_occupancy.h

/* Copyright (c) 2023 PaddlePaddle Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. */

#pragma once

#include <cuda_runtime_api.h>

#include "cutlass/device_kernel.h"
#include "paddle/phi/kernels/fusion/cutlass/utils/cuda_utils.h"

namespace phi {
template <typename GemmKernel>
inline int compute_occupancy_for_kernel() {
  int smem_size = static_cast<int>(sizeof(typename GemmKernel::SharedStorage));

  if (smem_size > (48 << 10)) {
    cudaError_t status =
        cudaFuncSetAttribute(cutlass::Kernel<GemmKernel>,
                             cudaFuncAttributeMaxDynamicSharedMemorySize,
                             smem_size);
    if (status == cudaError::cudaErrorInvalidValue) {
      // Clear the error bit since we can ignore this.
      // This should mean that smem_size >
      // cudaDevAttrMaxSharedMemoryPerBlockOptin. In that case, we return an
      // occupancy of 0. This will cause the heuristic to ignore this
      // configuration.
      status = cudaGetLastError();
      return 0;
    }
    check_cuda_error(status);
  }

  int max_active_blocks = -1;
  check_cuda_error(
      cudaOccupancyMaxActiveBlocksPerMultiprocessor(&max_active_blocks,
                                                    cutlass::Kernel<GemmKernel>,
                                                    GemmKernel::kThreadCount,
                                                    smem_size));

  return max_active_blocks;
}
}  // namespace phi