windows map file的内存粒度

 

map file最小粒度可以通过

void GetSystemInfo(
  LPSYSTEM_INFO lpSystemInfo
);
lpSystemInfo->dwPageSize

得到;基本上都是4K。那么,进行FileMapping的时候,只要分配的小于4K,系统都会按照4K来进行;例子为证:


void CMapViewDlg::OnCancel2()
{
    long lPageSize(10);
    AllocFileMapping(lPageSize);

}

const int MAP_SIZE = 7;
void CMapViewDlg::AllocFileMapping(int lPageSize)
{
    HANDLE hMap[MAP_SIZE];
    LPVOID lpMapView[MAP_SIZE];
    for ( int n = 0; n < MAP_SIZE; n++ )
    {
        // Create a new page with appointed page name and length
        CString csPage;
        csPage.Format(_T("Page%d"), n);
        hMap[n] = ::CreateFileMapping( INVALID_HANDLE_VALUE,
            NULL,
            PAGE_READWRITE,
            0,
            lPageSize,
            csPage );
       
        // MapView and save page info to
        lpMapView[n] = ::MapViewOfFile( hMap[n],
            FILE_MAP_ALL_ACCESS,
            0,
            0,
            0 );

        memset(lpMapView[n], n, lPageSize);
       
    }
    for ( n = 0; n < MAP_SIZE; n++ )
    {
        ::UnmapViewOfFile( lpMapView[n] );
        ::CloseHandle( hMap[n] );
        hMap[n] = NULL;
    }

}

结果是7*4K。

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