get_cache_size.cpp

// Author: Kim Walisch
// Released into public domain

#include <windows.h>
#include <cstdlib>

typedef BOOL (WINAPI *LPFN_GLPI)(PSYSTEM_LOGICAL_PROCESSOR_INFORMATION, PDWORD);

/// Get the CPU's cache size in bytes.
/// Works on Windows (MSVC, Intel C++ Compiler, Cygwin, ...).
/// @param level  1 for L1, 2 for L2, 3 for L3.
///
std::size_t get_cache_size(int level)
{
  LPFN_GLPI glpi = (LPFN_GLPI) GetProcAddress(GetModuleHandle(TEXT("kernel32")), "GetLogicalProcessorInformation");

  // GetLogicalProcessorInformation not supported
  if (glpi == NULL) 
    return 0;

  DWORD buffer_bytes = 0;
  std::size_t cache_size = 0;

  glpi(0, &buffer_bytes);
  std::size_t size = buffer_bytes / sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
  SYSTEM_LOGICAL_PROCESSOR_INFORMATION* buffer = new SYSTEM_LOGICAL_PROCESSOR_INFORMATION[size];
  glpi(buffer, &buffer_bytes);

  for (std::size_t i = 0; i < size; i++)
  {
    if (buffer[i].Relationship == RelationCache && 
        buffer[i].Cache.Level == level)
    {
      cache_size = buffer[i].Cache.Size;
      break;
    }
  }

  delete buffer;
  return cache_size;
}