Question

使用pthread_setschedparam API创建优先级为“ -15”的线程。但是失败并返回值EINVAL（根据MAN页：策略不是公认的策略，或者param对该策略没有意义。）N

正如我所知，进程的优先级可能会影响值（-19到20），但是我不知道进程中的线程的优先级范围是多少。需要专家帮助才能了解这一点。

class CRAII_Priority_Thread : public std::thread
{
    std::thread mDSIRecvThread;
    const int   mPolicy;
    sched_param mSchParams;

  public:
    CRAII_Priority_Thread(std::thread&& thr,const int policy, const int priority)
        : mDSIRecvThread{std::move(thr)}
        , mPolicy{policy}
        , mSchParams{priority}
    {
        sched_param currSchParams;
        int currPolicy = 0;
        if (pthread_getschedparam(mDSIRecvThread.native_handle(), &currPolicy, &currSchParams))
        {
            std::cout << "Failed to pthread_getschedparam: ERROR "  << std::strerror(errno) << "\n";
        }
        std::cout << "Current configuration DSIThread ["<< mDSIRecvThread.get_id()
                  << "] currPolicy [" << currPolicy << "] and PRIORITY ["
                  << currSchParams.sched_priority << "]\n";
        std::cout << "Trying to set configuration as DSIThread  ["<< mDSIRecvThread.get_id()
                  << "] currPolicy [" << mPolicy << "] and PRIORITY ["
                  << mSchParams.sched_priority << "]\n";

        int iRet = -1;
        if (iRet = pthread_setschedparam(mDSIRecvThread.native_handle(), mPolicy, &mSchParams))
        {
                switch(iRet)
                {
                        case ESRCH:
                                std::cout << "No thread with the ID thread could be found\n";
                        break;
                        case EINVAL:
                                std::cout << "policy is not a recognized policy, or param does not make sense for the policy.\n";
                        break;
                        case EPERM:
                                std::cout << "The caller does not have appropriate privileges to set the specified scheduling policy and parameters.\n";
                        break;
                        case ENOTSUP:
                                std::cout << "attempt was made to set the policy or scheduling parameters to an unsupported value\n";
                        break;
                        default:
                        break;
                }

            std::cout << "Return value [" << iRet << "] Failed to pthread_setschedparam: ERROR "  << std::strerror(errno) << "\n";
        }
if (pthread_getschedparam(mDSIRecvThread.native_handle(), &currPolicy, &currSchParams))
        {
            std::cout << "Failed to pthread_getschedparam: ERROR "  << std::strerror(errno) << "\n";
        }
        std::cout << "setconfiguration successfull current configuration  DSIThread ["<< mDSIRecvThread.get_id()
                  << "] currPolicy [" << currPolicy << "] and PRIORITY ["
                  << currSchParams.sched_priority << "]\n";
    }

    ~CRAII_Priority_Thread()
    {
        if (mDSIRecvThread.joinable())
        {
            mDSIRecvThread.join();
        }
        else
        {
            std::cout << "ERROR : Failed to join DSI recv thread\n";
        }
    }

  private:
    sched_param sch_params;
};

void thread_function()
{
        std::cout << __FUNCTION__ << "\n";
}
int main()
{
        CRAII_Priority_Thread(std::thread(&thread_function), 0, -15);
        return 0;
}

出现如下错误：

当前配置DSIThread [140333652039424] currPolicy [0]和   优先级[0]

尝试将配置设置为DSIThread [140333652039424] currPolicy   [0]和优先级[-15]

政策不是公认的政策，否则param对于   政策。 thread_function

返回值[22]失败至pthread_setschedparam：ERROR无效   论点

pthread_getschedparam失败：ERROR无效的参数   setconfiguration成功当前配置DSIThread   [140333652039424] currPolicy [0]和PRIORITY [0]

Answer 1

man sched_get_priority_max：

int sched_get_priority_max(int policy);
int sched_get_priority_min(int policy);
sched_get_priority_max()返回可与策略标识的调度算法一起使用的最大优先级值。 sched_get_priority_min()返回可与策略标识的调度算法一起使用的最小优先级值。受支持的策略值为SCHED_FIFO，SCHED_RR，SCHED_OTHER，SCHED_BATCH，SCHED_IDLE和SCHED_DEADLINE。

请注意，有效策略列表中未指定0。

Answer 2

并非eeorika的回答中的所有内容都是正确的。 sched_setscheduler的{{3}}这样说：

对于根据常规调度策略（SCHED_OTHER，SCHED_IDLE，SCHED_BATCH）之一调度的线程，sched_priority不在调度决策中（必须将其指定为0）。

并且调度策略0对应于SCHED_OTHER，这就是您的呼叫失败的原因。

我可能是错的，但是实际上似乎没有一种方法可以在没有root特权的情况下提高单个线程的优先级。另请参见documentation。

处理中的线程的最高优先级是什么？

2 个答案: