linux下设置线程优先级 http://blog.csdn.net/typhoonzb/article/details/4544278

在linux下我们可以通过

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,    void *(*start_routine)(void*), void *arg);来创建线程，但是如何设置线程的优先级呢？在讨论这个问题的时候，我们先要确定当前线程使用的调度策略，posix提供了int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy);函数来获取所使用的调度策略，它们是：SCHED_FIFO, SCHED_RR 和 SCHED_OTHER。我们可以使用int sched_get_priority_max(int policy);int sched_get_priority_min(int policy);来获取线程线程可是设置的最大和最小的优先级值，如果调用成功就返回最大和最小的优先级值，否则返回－1。从我现在运行的linux系统中，我使用下列程序获取了对应三种调度策略中的最大和最小优先级：policy = SCHED_OTHERShow current configuration of prioritymax_priority = 0min_priority = 0Show SCHED_FIFO of prioritymax_priority = 99min_priority = 1Show SCHED_RR of prioritymax_priority = 99min_priority = 1Show priority of current threadpriority = 0Set thread policySet SCHED_FIFO policypolicy = SCHED_FIFOSet SCHED_RR policypolicy = SCHED_RRRestore current policypolicy = SCHED_OTHER我们可以看到SCHED_OTHER是不支持优先级使用的，而SCHED_FIFO和SCHED_RR支持优先级的使用，他们分别为1和99，数值越大优先级越高。 从上面的结果我们可以看出，如果程序控制线程的优先级，一般是用pthread_attr_getschedpolicy来获取系统使用的调度策略，如果是SCHED_OTHER的话，表明当前策略不支持线程优先级的使用，否则可以。当然所设定的优先级范围必须在最大和最小值之间。我们可以通过sched_get_priority_max和sched_get_priority_min来获取。可能网友会问，是否我们可以通过int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);来设定自己所需的调度策略呢？我觉得是完全可以的（有些系统需要定义_POSIX_THREAD_PRIORITY_SCHEDULING），只要系统实现了对应的调用策略。说了半天，我们还没有说，在系统允许使用线程优先级别的时候，如何设置优先级别呢？int pthread_attr_setschedparam(pthread_attr_t *attr,     const struct sched_param *param);int pthread_attr_getschedparam(const pthread_attr_t *attr,     struct sched_param *param);上面两个函数分别用于设置线程的优先级，struct sched_param的定义如下struct sched_param{    int __sched_priority; //所要设定的线程优先级};使用的测试程序：

#include <iostream>
#include <pthread.h>
#include <sched.h>
#include <assert.h>

using namespace std;

static int get_thread_policy( pthread_attr_t &attr )
{
        int policy;
        int rs = pthread_attr_getschedpolicy( &attr, &policy );
        assert( rs == 0 );
        switch ( policy )
        {
        case SCHED_FIFO:
                cout << "policy = SCHED_FIFO" << endl;
                break;

        case SCHED_RR:
                cout << "policy = SCHED_RR" << endl;
                break;

        case SCHED_OTHER:
                cout << "policy = SCHED_OTHER" << endl;
                break;

        default:
                cout << "policy = UNKNOWN" << endl;
                break;
        }

        return policy;
}

static void show_thread_priority( pthread_attr_t &attr, int policy )
{
        int priority = sched_get_priority_max( policy );
        assert( priority != -1 );
        cout << "max_priority = " << priority << endl;

        priority = sched_get_priority_min( policy );
        assert( priority != -1 );
        cout << "min_priority = " << priority << endl;
}

static int get_thread_priority( pthread_attr_t &attr )
{
        struct sched_param param;

        int rs = pthread_attr_getschedparam( &attr, &param );
        assert( rs == 0 );
        cout << "priority = " << param.__sched_priority << endl;

        return param.__sched_priority;
}

static void set_thread_policy( pthread_attr_t &attr,  int policy )
{
        int rs = pthread_attr_setschedpolicy( &attr, policy );
        assert( rs == 0 );
        get_thread_policy( attr );
}

int main( void )
{
        pthread_attr_t attr;
        struct sched_param sched;
        int rs;

        rs = pthread_attr_init( &attr );
        assert( rs == 0 );

        int policy = get_thread_policy( attr );

        cout << "Show current configuration of priority" << endl;
        show_thread_priority( attr, policy );

        cout << "Show SCHED_FIFO of priority" << endl;
        show_thread_priority( attr, SCHED_FIFO );

        cout << "Show SCHED_RR of priority" << endl;
        show_thread_priority( attr, SCHED_RR );

        cout << "Show priority of current thread" << endl;
        int priority = get_thread_priority( attr );

        cout << "Set thread policy" << endl;
        cout << "Set SCHED_FIFO policy" << endl;
        set_thread_policy( attr, SCHED_FIFO );
        cout << "Set SCHED_RR policy" << endl;
        set_thread_policy( attr, SCHED_RR );
        cout << "Restore current policy" << endl;
        set_thread_policy( attr, policy );


        rs = pthread_attr_destroy( &attr );
        assert( rs == 0 );

        return 0;
}