CODEWITHSUNDEEP
c++windowsprocessthread-priority
alena_fox_spb
alena_fox_spb

Reputation: 737

Process and thread priority in windows 7

I have a simple "training" project wich must show the priority mechanism in Windows.

This is my C++ code:

#include <stdio.h>
#include <windows.h>
DWORD WINAPI Thread1(LPVOID);
int stop;
int sleep = 10000;
struct params {
    int num;
    bool* runflg;
};
long long counters[7] = {0,0,0,0,0,0,0};
int priority[7] = {THREAD_PRIORITY_IDLE,  THREAD_PRIORITY_LOWEST,  THREAD_PRIORITY_BELOW_NORMAL,  THREAD_PRIORITY_NORMAL, THREAD_PRIORITY_ABOVE_NORMAL, THREAD_PRIORITY_HIGHEST, THREAD_PRIORITY_TIME_CRITICAL};
int main(int argc, char* argv[])
{
        int thrds;
        if (argc < 2) stop = 5;
        else stop = atoi(argv[1]);  

         bool runFlag = true;
         __int64 end_time;
         LARGE_INTEGER end_time2;

        HANDLE tm1 = CreateWaitableTimer(NULL, false, NULL);
        end_time = -1 * stop * 10000000;
        end_time2.LowPart = (DWORD) (end_time & 0xFFFFFFFF);
        end_time2.HighPart = (LONG) (end_time >> 32);
        SetWaitableTimer(tm1, &end_time2, 0,NULL, NULL, false); 

        //SetPriorityClass(GetCurrentProcess(), HIGH_PRIORITY_CLASS);
        printf("process priority = %d \n", GetPriorityClass(GetCurrentProcess()));
        SetProcessPriorityBoost(GetCurrentProcess(), true);

        for (int i = 0; i < 7; i++) {
            DWORD targetThreadId;
            params* param = (params*)malloc(sizeof(params));
            param->num = i;
            param->runflg = &runFlag;
            HANDLE t1 = CreateThread(NULL, 0, Thread1, param, 0, &targetThreadId);
            SetThreadPriority(t1, priority[i]); //задание приоритета

            PBOOL ptr1 = (PBOOL)malloc(sizeof(BOOL));
            GetThreadPriorityBoost(t1, ptr1);
            SetThreadPriorityBoost(t1, true); //запрет динамического изм. приоритета

            CloseHandle(t1);
        }
        WaitForSingleObject(tm1,INFINITE);
        runFlag = false;
        CloseHandle(tm1);
        printf("\n");
        for (int i = 0; i < 7; i++) {
            printf("%d - %ld\n",i,  counters[i]);
        }
        return 0;
}
DWORD WINAPI Thread1(LPVOID prm) 
{       
    params arg = *((params*)prm);
    printf("thread # %d priority  = %d \n", arg.num, GetThreadPriority(GetCurrentThread()));

    while(1) {          
            counters[arg.num]++;
            Sleep(0);
            if(*(arg.runflg) == false)
                break;
    }   
    return 0;
}

In the code, I create 7 threads with different thread priorities. Every thread has its own counter. The program should run for about 5 seconds, and after that the console must show the threads' priorities and their values. When I did it a year ago on Win XP 32 everything was working - a thread with less priority has a smaller counter value. But now I have strange results like this:

process priority = 32

thread # 0 priority  = -15
thread # 1 priority  = -2
thread # 2 priority  = -1
thread # 3 priority  = 0
thread # 4 priority  = 1
thread # 5 priority  = 2
thread # 6 priority  = 15

0 - 5401405
1 - 5726804
2 - 6676367
3 - 8320768
4 - 3223481
5 - 3085247
6 - 3177885

Why are priority levels not working and counters have such strange values (not sorted ascending)?

Upvotes: 1

Views: 1258

Answers (1)

alena_fox_spb
alena_fox_spb

Reputation: 737

How has say @Zilog in answers to this question - the reason of some strange actions is in MULTI-procces CPU.

If someone want to see how threads with different priority work - they must use specific utulity (like monitor\profilier of system working), or in program use special func-s, wich use only one processor.

Upvotes: 1

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