Creating a File Mapping Using Large Pages

The following example uses the CreateFileMapping function with the SEC_LARGE_PAGES flag to use large pages. The buffer must be large enough to contain the minimum size of a large page. This value is obtained using the GetLargePageMinimum function. This feature also requires the "SeLockMemoryPrivilege" privilege.

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

#define BUF_SIZE 65536

TCHAR szName[]=TEXT("LARGEPAGE");
typedef int (*GETLARGEPAGEMINIMUM)(void);

void DisplayError(const wchar_t* pszAPI, DWORD dwError)
{
 LPVOID lpvMessageBuffer;

 FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
 FORMAT_MESSAGE_FROM_SYSTEM |
 FORMAT_MESSAGE_IGNORE_INSERTS,
 NULL, dwError,
 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 (LPTSTR)&lpvMessageBuffer, 0, NULL);

 //... now display this string
 _tprintf(TEXT("ERROR: API = %s\n"), pszAPI);
 _tprintf(TEXT(" error code = %d\n"), dwError);
 _tprintf(TEXT(" message = %s\n"), lpvMessageBuffer);

 // Free the buffer allocated by the system
 LocalFree(lpvMessageBuffer);

 ExitProcess(GetLastError());
}

void Privilege(const wchar_t* pszPrivilege, BOOL bEnable)
{
 HANDLE hToken;
 TOKEN_PRIVILEGES tp;
 BOOL status;
 DWORD error;

 // open process token
 if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken))
 DisplayError(TEXT("OpenProcessToken"), GetLastError());

 // get the luid
 if (!LookupPrivilegeValue(NULL, pszPrivilege, &tp.Privileges[0].Luid))
 DisplayError(TEXT("LookupPrivilegeValue"), GetLastError());

 tp.PrivilegeCount = 1;

 // enable or disable privilege
 if (bEnable)
 tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
 else
 tp.Privileges[0].Attributes = 0;

 // enable or disable privilege
 status = AdjustTokenPrivileges(hToken, FALSE, &tp, 0, (PTOKEN_PRIVILEGES)NULL, 0);

 // It is possible for AdjustTokenPrivileges to return TRUE and still not succeed.
 // So always check for the last error value.
 error = GetLastError();
 if (!status || (error != ERROR_SUCCESS))
 DisplayError(TEXT("AdjustTokenPrivileges"), GetLastError());

 // close the handle
 if (!CloseHandle(hToken))
 DisplayError(TEXT("CloseHandle"), GetLastError());
}

int _tmain(void)
{
 HANDLE hMapFile;
 LPCTSTR pBuf;
 DWORD size;
 GETLARGEPAGEMINIMUM pGetLargePageMinimum;
 HINSTANCE hDll;

 // call succeeds only on Windows Server 2003 SP1 or later
 hDll = LoadLibrary(TEXT("kernel32.dll"));
 if (hDll == NULL)
 DisplayError(TEXT("LoadLibrary"), GetLastError());

 pGetLargePageMinimum = (GETLARGEPAGEMINIMUM)GetProcAddress(hDll,
 "GetLargePageMinimum");
 if (pGetLargePageMinimum == NULL)
 DisplayError(TEXT("GetProcAddress"), GetLastError());

 size = (*pGetLargePageMinimum)();

 FreeLibrary(hDll);

 _tprintf(TEXT("Page Size: %u\n"), size);

 Privilege(TEXT("SeLockMemoryPrivilege"), TRUE);

 hMapFile = CreateFileMapping(
 INVALID_HANDLE_VALUE, // use paging file
 NULL, // default security
 PAGE_READWRITE | SEC_COMMIT | SEC_LARGE_PAGES,
 0, // max. object size
 size, // buffer size
 szName); // name of mapping object

 if (hMapFile == NULL)
 DisplayError(TEXT("CreateFileMapping"), GetLastError());
 else
 _tprintf(TEXT("File mapping object successfully created.\n"));

 Privilege(TEXT("SeLockMemoryPrivilege"), FALSE);

 pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object
 FILE_MAP_ALL_ACCESS | FILE_MAP_LARGE_PAGES, // read/write permission
 0,
 0,
 BUF_SIZE);

 if (pBuf == NULL)
 DisplayError(TEXT("MapViewOfFile"), GetLastError());
 else
 _tprintf(TEXT("View of file successfully mapped.\n"));

 // do nothing, clean up an exit
 UnmapViewOfFile(pBuf);
 CloseHandle(hMapFile);
}

Related topics

Creating a File Mapping Object

Large Page Support