很好（）用于更改线程优先级或进程优先级？

The man page for nice says "nice() adds inc to the nice value for the calling process. So, can we use it to change the nice value for a thread created by pthread_create?

nice的手册页说“nice（）”将inc添加到调用进程的nice值。那么，我们可以用它来改变pthread_create创建的线程的nice值吗？

EDIT: It seems that we do can set the nice value per thread.

编辑：我们似乎可以为每个线程设置好的值。

I wrote a application ,setting different nice value for different thread, and observed that the "nicer" thread has been scheduled with lower priority. Checking the output, I found that the string "high priority ................" get outputted more frequently.

我写了一个应用程序，为不同的线程设置了不同的好价值，并观察到“更好”的线程已被安排在较低的优先级。检查输出，我发现字符串“高优先级................”更频繁地输出。

void * thread_function1(void *arg)
{

 pid_t tid = syscall(SYS_gettid);

 int ret = setpriority(PRIO_PROCESS, tid, -10);
 printf("tid of high priority thread %d , %d\n",tid ,getpriority(PRIO_PROCESS,tid));
 while(1){
  printf("high priority ................\n");
    }

}


void * thread_function(void *arg)
{
 pid_t tid = syscall(SYS_gettid);
 int ret = setpriority(PRIO_PROCESS, tid, 10);
 printf("tid of low priority thread %d , %d \n",tid ,getpriority(PRIO_PROCESS,tid));
while(1) 
{

  printf("lower priority\n");
}
}


int main()
{

pthread_t id1;
pthread_t id2;

pid_t pid = getpid();
pid_t tid = syscall(SYS_gettid);

printf("main thread : pid = %d , tid = %d \n" , pid, tid);
pthread_create(&id1, NULL, thread_function1,  NULL);
pthread_create(&id2, NULL,thread_function,   NULL);

pthread_join(id1, NULL);
pthread_join(id2, NULL);


}

1 个解决方案

#1

The pthreads man page says:

pthreads手册页说：

POSIX.1 also requires that threads share a range of other attributes (i.e., these attributes are process-wide rather than per-thread):

POSIX.1还要求线程共享一系列其他属性（即，这些属性是进程范围而不是每个线程）：

[...]

[...]

nice value (setpriority(2))

好的价值（setpriority（2））

So, theoretically, the "niceness" value is global to the process and shared by all threads, and you should not be able to set a specific niceness for one or more individual threads.

因此，从理论上讲，“niceness”值对于进程是全局的并且由所有线程共享，并且您不应该为一个或多个单独的线程设置特定的好处。

However, the very same man page also says:

但是，同样的手册页也说：

LinuxThreads

Linux线程

The notable features of this implementation are the following:

此实现的显着特征如下：

[...]

[...]

Threads do not share a common nice value.

线程不共享一个常见的nice值。

NPTL

NPTL

[...]

[...]

NPTL still has a few non-conformances with POSIX.1:

NPTL仍然与POSIX.1有一些不符合：

Threads do not share a common nice value.

线程不共享一个常见的nice值。

So it turns out that both threading implementations on Linux (LinuxThreads and NPTL) actually violate POSIX.1, and you can set a specific niceness for one or more individual threads by passing a tid to setpriority() on these systems.

因此，事实证明Linux上的线程实现（LinuxThreads和NPTL）实际上都违反了POSIX.1，并且您可以通过在这些系统上将tid传递给setpriority（）来为一个或多个单独线程设置特定的好处。

#1