Question

我正在尝试使用SCHED_RR设置pthread的优先级，以便当较高优先级的任务准备运行时，较低优先级的任务将不会获得cpu时间。我的系统是Ubuntu 18.04.1 LTS配置（没有特殊的内核选项）。

在测试用例中，两个任务都实时共享，而高优先级任务已准备好运行。

该测试用例创建了两个线程，每个线程短暂地睡眠然后继续。低优先级线程尝试每秒创建文本输出。我的期望是，低优先级线程不产生任何输出，而高优先级线程准备运行几秒钟。输出显示实时正在共享。

即使我以root身份运行代码（即sudo ./ThreadTest），也会发生这种情况

#include <iostream>
#include <error.h>
#include <pthread.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

using namespace std;

// Thread function designed to use all realtime it can get intended to be started
// at high priority.  Prints once per second if it can.
void * BackGroundThread(void *)
{
    struct timespec now;
    cout << "Low priority task start" << endl;
    sleep(1);
    clock_gettime(CLOCK_MONOTONIC, &now);
    int32_t intStartSec = now.tv_sec;

    for (int i = 0; i < 10; i++)
    {
        do
        {
            clock_gettime(CLOCK_MONOTONIC, &now);
        } while (intStartSec == now.tv_sec); // Wait for second boundary.
        cout << "Low priority task i( " << i << " ) " << " Time( " << now.tv_sec
                << ", " << now.tv_nsec << " )" << endl;
        intStartSec = now.tv_sec;
    }
    cout << "Low priority task end." << endl;
    return NULL;
}
// Thread function designed to use all realtime it can get intended to be started
// at high priority.  Prints once per second.
void * HighPriorityThread(void *)
{
    sleep(3);
    cout << "High priority task start." << endl;
    volatile int y = 0;
    do
    {
        y++;
    } while (y != 0); // Wait for second boundary.
    cout << "High priority task end." << endl;
    return NULL;
}

pthread_t * CreateRRThreadWithPriority(pthread_t *myThread, int priority,
        void *(*start_routine)(void *))
{
    int retVal = -1;
    pthread_attr_t workingAttrib;
    struct sched_param prioParam;
    prioParam.sched_priority = priority;
    retVal = pthread_attr_init(&workingAttrib);
    if (retVal)
    {
        cout << "CreateRRThreadWithPriority: Failure from pthread_attr_init: "
                << strerror(retVal) << endl;
    }
    retVal = pthread_attr_setschedpolicy(&workingAttrib, SCHED_RR);
    if (retVal)
    {
        cout
                << "CreateRRThreadWithPriority: Failure from thread_attr_setschedpolic: "
                << strerror(retVal) << endl;
    }
    retVal = pthread_attr_setschedparam(&workingAttrib, &prioParam);
    if (retVal)
    {
        cout
                << "CreateRRThreadWithPriority: Failure from pthread_attr_setschedparam: "
                << strerror(retVal) << endl;
    }
    retVal = pthread_create(myThread, &workingAttrib, start_routine, NULL);
    if (retVal)
    {
        cout << "CreateRRThreadWithPriority: Failure from pthread_create: "
                << strerror(retVal) << endl;
    }
    return myThread;
}

int main()
{
    cout << "Thread Test" << endl; // prints Thread Test
    cout << sched_get_priority_min(SCHED_RR) << endl;
    cout << sched_get_priority_max(SCHED_RR) << endl;
    pthread_t LP, HP;
    CreateRRThreadWithPriority(&LP, sched_get_priority_min(SCHED_RR),
            BackGroundThread);
    CreateRRThreadWithPriority(&HP, sched_get_priority_max(SCHED_RR),
            HighPriorityThread);
    pthread_join(LP, NULL);
    pthread_join(HP, NULL);
    cout << "Complete" << endl;
    return 0;
}

输出：

Thread Test
1
99
Low priority task start
Low priority task i( 0 )  Time( 11093, 13 )
Low priority task i( 1 )  Time( 11094, 17 )
High priority task start.
Low priority task i( 2 )  Time( 11095, 3 )
Low priority task i( 3 )  Time( 11096, 4 )
Low priority task i( 4 )  Time( 11097, 16 )
Low priority task i( 5 )  Time( 11098, 8 )
Low priority task i( 6 )  Time( 11099, 14 )
Low priority task i( 7 )  Time( 11100, 1 )
Low priority task i( 8 )  Time( 11101, 5 )
High priority task end.
Low priority task i( 9 )  Time( 11102, 2 )
Low priority task end.
Complete

其他信息： 考虑到低优先级任务能够运行，因为有多个内核，因此我将高优先级任务的数量增加到12个。低优先级任务继续运行，而同时运行了12个高优先级任务。我缺少什么？有内核设置吗？

无法在Ubuntu桌面应用程序上设置pthread优先级

0 个答案: