my code to prove working set larger than virtual bytes

[George2]

Hello everyone,


From the definition of working set, it is a subset of virtual pages resident in physical memory -- from book Windows Internals. It means working set could not be larger than virtual memory (subset relationship).

But the following simple code on Windows Server 2003 proves (if you monitor virtual bytes counter and working set bytes conuter from perfmon), if we do not unmap the page map file, the working set will continue to increase (and much larger than virtual bytes) until we unmap it.

Take a breakpoint before following code section,

            // close mapped files to avoid leak
            for (sectionIndex = 0; sectionIndex < size/allocSize; sectionIndex++)
            {
                if (map [sectionIndex])
                { 
                    UnmapViewOfFile(map [sectionIndex]);
                }
            }
 

Any ideas? Does my code break the definition of working set? Why working set is much larger than virtual bytes?

#include <windows.h> 
#include <stdio.h> 
 
int main(int argc, char* argv[]) 
{ 
    LARGE_INTEGER start,end; 
    LARGE_INTEGER freq; 
    QueryPerformanceCounter(&start); 
    QueryPerformanceFrequency(&freq); 
 
    MEMORYSTATUS memstat; 
    void** map;
    int sectionIndex = 0;
    memstat.dwLength = sizeof(memstat); 
    GlobalMemoryStatus(&memstat); 
 
    // basic file mapping test (512 MB) 
    long long size = 512*1024*1024; 
 
    HANDLE mapping = 
    CreateFileMapping(NULL,NULL,PAGE_READWRITE|SEC_COMMIT,(DWORD)(size>>32),DWORD(size),NULL); 
    if (mapping) 
    { 
        // create and destroy temporary views 
        SYSTEM_INFO sysInfo; 
        GetSystemInfo(&sysInfo); 
        const int allocSize = sysInfo.dwAllocationGranularity; 
 
        GlobalMemoryStatus(&memstat); 
 
        void *mem = new char[allocSize]; 
        memset(mem,0x11,allocSize); 
 
        map = (void**) new char [sizeof(void*) * size / allocSize];
 
        for (int i=0; i<10; i++) 
        { 
 
            sectionIndex = 0;
            for (long long offset=0; offset<=size-allocSize; offset+=allocSize) 
            { 
                map [sectionIndex] = 
                MapViewOfFile(mapping,FILE_MAP_WRITE,(DWORD)(offset>>32),(DWORD)offset,allocSize); 
                if (map [sectionIndex]) 
                { 
                    memcpy(map [sectionIndex],mem,allocSize); 
                    // UnmapViewOfFile(map);
                }
 
                sectionIndex++;
            } // for (long long offset=0; offset<=size-allocSize; offset+=allocSize) 
 
            // close mapped files to avoid leak
            for (sectionIndex = 0; sectionIndex < size/allocSize; sectionIndex++)
            {
                if (map [sectionIndex])
                { 
                    UnmapViewOfFile(map [sectionIndex]);
                }
            }
 
            GlobalMemoryStatus(&memstat); 
 
            sectionIndex = 0;
            for (long long offset=0; offset<=size-allocSize; offset+=allocSize) 
            { 
                map [sectionIndex] = 
                MapViewOfFile(mapping,FILE_MAP_READ,(DWORD)(offset>>32),(DWORD)offset,allocSize); 
                if (map [sectionIndex]) 
                { 
                    for (int t=0; t<allocSize; t++) 
                    { 
                        if (((char *)(map [sectionIndex]))[t]!=0x11) 
                        { 
                            OutputDebugString("Memory read failed\n"); 
                        } 
                    } 
                } 
 
                UnmapViewOfFile(map [sectionIndex]);
            } 
 
            // close mapped files to avoid leak
            /*
            for (sectionIndex = 0; sectionIndex < size/allocSize; sectionIndex++)
            {
                if (map [sectionIndex])
                { 
                    UnmapViewOfFile(map [sectionIndex]);
                }
            }
            */
 
            GlobalMemoryStatus(&memstat); 
        } // for (int i=0; i<10; i++)
 
        QueryPerformanceCounter(&end); 
 
        GlobalMemoryStatus(&memstat); 
 
        printf("Time %.3f\n", 
        double(end.QuadPart-start.QuadPart)/double(freq.QuadPart)); 
        CloseHandle(mapping); 
        delete[] mem; 
        GlobalMemoryStatus(&memstat); 
    } //if (mapping)
 
    return 0;
} 
 

thanks in advance,
George