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POProcess and thread priority in windows 7
 

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  1. POProcess and thread priority in windows 7
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    <p>I have a simple "training" project wich must show the priority mechanism in Windows.</p> <p>This is my C++ code:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;windows.h&gt; 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 &lt; 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 &amp; 0xFFFFFFFF); end_time2.HighPart = (LONG) (end_time &gt;&gt; 32); SetWaitableTimer(tm1, &amp;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 &lt; 7; i++) { DWORD targetThreadId; params* param = (params*)malloc(sizeof(params)); param-&gt;num = i; param-&gt;runflg = &amp;runFlag; HANDLE t1 = CreateThread(NULL, 0, Thread1, param, 0, &amp;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 &lt; 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; } </code></pre> <p>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:</p> <pre><code>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 </code></pre> <p>Why are priority levels not working and counters have such strange values (not sorted ascending)?</p>
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    1. COThread priority is just a hint, this program could really output anything (especially if you use Sleep).
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    2. CO@user2802841, i asked about counters values, not about hint values of each priorities. Counter values must be "sorted ascending" when thread priorities are like in this program
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    3. CO@alena-fox-spb this is exactly what I'm talking about, in your program as currently written there is no guarantee that your counter values will be lower for threads with lower priority (or "sorted ascending"). Especially since you use `Sleep` which docs say: _"Note that a ready thread is not guaranteed to run immediately. Consequently, the thread may not run until some time after the sleep interval elapses."_ Both of those can cause your counter values to be anything, lowest priority thread can just as well have hightest counter value.
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