Pthread_setaffinity_np causes performance degradation for allocating tensor

C++
1

Hi. I got some weird issue about pthread_setaffinity_np and Tensor allocation.

Hardware
  Intel(R) Xeon(R) CPU Gold 5218 x 2
  Nvidia Titan RTX

Software
  Ubuntu 20.04
  Pytorch v1.9.0
  CUDA 11.3
  CUDNN 8.2.1

Below is my program code snippet.

#include <torch/script.h>
#include <torch/cuda.h>
#include <chrono>
#include <iostream>
#include <thread>
#include <pthread.h>
#include <cuda_runtime_api.h>

void create()
{
  auto options = torch::TensorOptions();

  while(true) {
    std::vector<torch::jit::IValue> inputs;
    long start_time = now(); // now() is my function that use chrono library and steady_clock
    auto tensor= torch::ones({1, 3, 224, 224}, torch::TensorOptions().pinned_memory(true));
    long end_time = now();
    std::cout << (end_time - start_time) << std::endl;
  }
}

int main(int argc, char* argv[])
{
  std::thread crt(create);

//  cpu_set_t cpuset;
//  CPU_ZERO(&cpuset);
//  CPU_SET(0, &cpuset);
//
//  int s = pthread_setaffinity_np(crt.native_handle(), sizeof(cpu_set_t), &cpuset);

  crt.join();


  return 0;
}

When i run this program, the time for creating tensor is under 1ms. (almost 0.01ms)

But, if i remove // and make that code lines work, the time result increases extreamely. (60ms ~ 100ms and more)

I also use under command. That is normal.

taskset -c 0 ./program

Can you give me some advice for this issue?