Process Explorer: Process Properties->Performance tab performance issue

ws.cpp

#include <Windows.h>
#include <psapi.h>


int main()
{
    HANDLE ProcessHandle;
    ULONG Processes[4096];
    ULONG DataSize;
    ULONG NumberOfProcesses;
    ULONG i;

    for ( ; ; ) {

        if (!EnumProcesses(Processes, sizeof(Processes), &DataSize)) {

            return 1;
        }

        NumberOfProcesses = DataSize / sizeof(ULONG);

        for (i = 0; i < NumberOfProcesses; i++) {

            ProcessHandle = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ,
                                        FALSE,
                                        Processes[i]);

            if (ProcessHandle) {

                PSAPI_WORKING_SET_INFORMATION WorkingSetInformation;
                PPSAPI_WORKING_SET_INFORMATION Buffer = NULL;
                ULONG BufferSize = 0;
                ULONG LastError;
                BOOL IsOk;

#if 1

                //
                // This is the current approach to get working set information in Process Explorer v16.22 in Process Properties dialog.
                // For a process with working set 10 GB it takes 1281 ((((10 * 1024 * 1024 * 1024) / 4096) * 8 + 8) / 16384 + 1) loops to get working set information.
                // Note that in main window it uses allocated buffer from the first process query and if the process's working set were increased it will add 0x4000
                // to the current buffer size, so the issue is slightly mitigated.
                //

                for ( ; ; ) {

                    IsOk = QueryWorkingSet(ProcessHandle, Buffer, BufferSize);

                    if (IsOk && Buffer && ((((ULONG)Buffer->NumberOfEntries * RTL_FIELD_SIZE(PSAPI_WORKING_SET_INFORMATION, NumberOfEntries)) + FIELD_OFFSET(PSAPI_WORKING_SET_INFORMATION, WorkingSetInfo)) <= BufferSize)) {

                        break;
                    }

                    if (Buffer) {

                        HeapFree(GetProcessHeap(), 0, Buffer);

                        Buffer = NULL;
                    }

                    LastError = GetLastError();

                    if (LastError != ERROR_BAD_LENGTH) {

                        break;
                    }

                    BufferSize += 0x4000;

                    Buffer = (PPSAPI_WORKING_SET_INFORMATION)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, BufferSize);
                }

#else

                //
                // This is the approach with one loop.
                //

                for ( ; ; ) {

                    Buffer = &WorkingSetInformation;
                    BufferSize = sizeof(WorkingSetInformation);

                    IsOk = QueryWorkingSet(ProcessHandle, Buffer, BufferSize);

                    if (IsOk) {

                        break;
                    }

                    LastError = GetLastError();

                    if (LastError != ERROR_BAD_LENGTH) {

                        break;
                    }

                    if (!Buffer->NumberOfEntries) {

                        break;
                    }

                    BufferSize = ((ULONG)Buffer->NumberOfEntries * RTL_FIELD_SIZE(PSAPI_WORKING_SET_INFORMATION, NumberOfEntries)) + FIELD_OFFSET(PSAPI_WORKING_SET_INFORMATION, WorkingSetInfo);

                    Buffer = (PPSAPI_WORKING_SET_INFORMATION)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, BufferSize);

                    if (Buffer) {

                        IsOk = QueryWorkingSet(ProcessHandle, Buffer, BufferSize);

                        if (IsOk) {

                            break;
                        }
                        else {

                            HeapFree(GetProcessHeap(), 0, Buffer);

                            Buffer = NULL;
                        }
                    }
                }

#endif

                if (Buffer && (Buffer != &WorkingSetInformation)) {

                    HeapFree(GetProcessHeap(), 0, Buffer);

                    Buffer = NULL;
                }

                CloseHandle(ProcessHandle);
            }
        }

        Sleep(1000);
    }

    return 0;
}