C++ threaded read test

thread_read_test.cpp

#include <thread>
#include <fstream>
#include <vector>
#include <chrono>
#include <sys/stat.h>
#include <iostream>
#include <atomic>

long file_size(const char* file)
{
    struct stat stat_buf;
    int rc = stat(file, &stat_buf);
    return rc == 0 ? stat_buf.st_size : -1;
}

int main(int argc, char** argv)
{
  system("echo 3 > /proc/sys/vm/drop_caches");

  long total_size = 0;

  auto thread_for_file = [&](const char* file) {
    total_size += file_size(file);
    return [=] {
      std::ifstream f;
      f.open(file);

      char buffer[2<<19];
      while(f.read(buffer, sizeof(buffer)));
    };
  };

  auto timer1 = std::chrono::high_resolution_clock::now();
  std::vector<std::thread> threads;
  for(int i = 1; i < argc;++i) {
    threads.emplace_back(std::thread(thread_for_file(argv[i])));
  }

  for(auto &thread: threads) {
    thread.join();
  }

  auto timer2 = std::chrono::high_resolution_clock::now();
  auto total_ms = std::chrono::duration_cast<std::chrono::milliseconds>(timer2 - timer1);
  double MBs = (((double)total_size)/1024/1024);
  double s = ((double)total_ms.count()/1000);
  std::cout << "Read " << MBs << " MBs in " << s << "s (" << (MBs/s) << " MB/s)\n";
  

  return 0;
}