test_shared_pointer_overhead.cpp

/*
Linux ext4:
743004324000
778425979000 (+4.76%)

Win8.1 NTFS:
17565970224000
17890031536128 (+1.8%)
*/

#include <iostream>
#include <memory>

/* timing.h

*/

#ifndef TIMING_H
#define TIMING_H

#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
typedef unsigned __int64 usCount;
static usCount GetUsCount()
{
  static LARGE_INTEGER ticksPerSec;
  static double scalefactor;
  LARGE_INTEGER val;
  if (!scalefactor)
  {
    if (QueryPerformanceFrequency(&ticksPerSec))
      scalefactor = ticksPerSec.QuadPart / 1000000000000.0;
    else
      scalefactor = 1;
  }
  if (!QueryPerformanceCounter(&val))
    return (usCount)GetTickCount() * 1000000000;
  return (usCount)(val.QuadPart / scalefactor);
}
#else
#include <sys/time.h>
#include <time.h>
#include <fcntl.h>
#include <unistd.h>
typedef unsigned long long usCount;
static usCount GetUsCount()
{
#ifdef CLOCK_MONOTONIC
  struct timespec ts;
  clock_gettime(CLOCK_MONOTONIC, &ts);
  return ((usCount)ts.tv_sec * 1000000000000LL) + ts.tv_nsec * 1000LL;
#else
  struct timeval tv;
  gettimeofday(&tv, 0);
  return ((usCount)tv.tv_sec * 1000000000000LL) + tv.tv_usec * 1000000LL;
#endif
}
#endif
#endif

int main(void)
{
  usCount begin = GetUsCount(), end;
  while (GetUsCount() - begin<3000000000000ULL);

  begin = GetUsCount();
  for (size_t n = 0; n < 1000000; n++)
  {
#ifdef WIN32
    auto h = CreateFile(L"test.txt", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (!h) throw std::runtime_error("foo");
    if(!CloseHandle(h)) throw std::runtime_error("foo");
#else
    int h = open("test.txt", O_RDONLY);
    if (h == -1) throw std::runtime_error("foo");
    if (-1 == close(h)) throw std::runtime_error("foo");
#endif
  }
  end = GetUsCount();
  usCount result1 = end - begin;

  begin = GetUsCount();
  for (size_t n = 0; n<1000000; n++)
  {
    volatile auto _h = std::make_shared<int>(5);
#ifdef WIN32
    auto h = CreateFile(L"test.txt", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (!h) throw std::runtime_error("foo");
    if (!CloseHandle(h)) throw std::runtime_error("foo");
#else
    int h = open("test.txt", O_RDONLY);
    if (h == -1) throw std::runtime_error("foo");
    if (-1 == close(h)) throw std::runtime_error("foo");
#endif
  }
  end = GetUsCount();
  usCount result2 = end - begin;

  std::cout << result1 << std::endl;
  std::cout << result2 << std::endl;
  return 0;
}