pthread_setschedparam(设置线程的优先级)
【摘要】
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...
在linux下我们可以通过
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int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
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void *(*start_routine)(void*), void *arg);
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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
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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_OTHER
-
Show current configuration of priority
-
max_priority = 0
-
min_priority = 0
-
Show SCHED_FIFO of priority
-
max_priority = 99
-
min_priority = 1
-
Show SCHED_RR of priority
-
max_priority = 99
-
min_priority = 1
-
Show priority of current thread
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priority = 0
-
Set thread policy
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Set SCHED_FIFO policy
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policy = SCHED_FIFO
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Set SCHED_RR policy
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policy = SCHED_RR
-
Restore current policy
-
policy = 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?
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int pthread_attr_setschedparam(pthread_attr_t *attr,
-
const struct sched_param *param);
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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
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struct sched_param
-
{
-
int __sched_priority; //所要设定的线程优先级
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};
使用的测试程序:
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#include <iostream>
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#include <pthread.h>
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#include <sched.h>
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#include <assert.h>
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using namespace std;
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-
static int get_thread_policy( pthread_attr_t &attr )
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{
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int policy;
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int rs = pthread_attr_getschedpolicy( &attr, &policy );
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assert( rs == 0 );
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switch ( policy )
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{
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case SCHED_FIFO:
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cout << "policy = SCHED_FIFO" << endl;
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break;
-
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case SCHED_RR:
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cout << "policy = SCHED_RR" << endl;
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break;
-
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case SCHED_OTHER:
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cout << "policy = SCHED_OTHER" << endl;
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break;
-
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default:
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cout << "policy = UNKNOWN" << endl;
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break;
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}
-
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return policy;
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}
-
-
static void show_thread_priority( pthread_attr_t &attr, int policy )
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{
-
int priority = sched_get_priority_max( policy );
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assert( priority != -1 );
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cout << "max_priority = " << priority << endl;
-
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priority = sched_get_priority_min( policy );
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assert( priority != -1 );
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cout << "min_priority = " << priority << endl;
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}
-
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static int get_thread_priority( pthread_attr_t &attr )
-
{
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struct sched_param param;
-
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int rs = pthread_attr_getschedparam( &attr, ¶m );
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assert( rs == 0 );
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cout << "priority = " << param.__sched_priority << endl;
-
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return param.__sched_priority;
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}
-
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static void set_thread_policy( pthread_attr_t &attr, int policy )
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{
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int rs = pthread_attr_setschedpolicy( &attr, policy );
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assert( rs == 0 );
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get_thread_policy( attr );
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}
-
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int main( void )
-
{
-
pthread_attr_t attr;
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struct sched_param sched;
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int rs;
-
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rs = pthread_attr_init( &attr );
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assert( rs == 0 );
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int policy = get_thread_policy( attr );
-
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cout << "Show current configuration of priority" << endl;
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show_thread_priority( attr, policy );
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cout << "Show SCHED_FIFO of priority" << endl;
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show_thread_priority( attr, SCHED_FIFO );
-
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cout << "Show SCHED_RR of priority" << endl;
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show_thread_priority( attr, SCHED_RR );
-
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cout << "Show priority of current thread" << endl;
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int priority = get_thread_priority( attr );
-
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cout << "Set thread policy" << endl;
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cout << "Set SCHED_FIFO policy" << endl;
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set_thread_policy( attr, SCHED_FIFO );
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cout << "Set SCHED_RR policy" << endl;
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set_thread_policy( attr, SCHED_RR );
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cout << "Restore current policy" << endl;
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set_thread_policy( attr, policy );
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-
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rs = pthread_attr_destroy( &attr );
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assert( rs == 0 );
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return 0;
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}
文章来源: allen5g.blog.csdn.net,作者:CodeAllen的博客,版权归原作者所有,如需转载,请联系作者。
原文链接:allen5g.blog.csdn.net/article/details/118683784
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