初始化/销毁线程属性
int pthread_attr_init(pthread_attr_t *attr); int pthread_attr_destroy(pthread_attr_t *attr);
线程分离属性
int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate); int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate);
参数说明：
The following values may be specified in detachstate:
PTHREAD_CREATE_DETACHED
Threads that are created using attr will be created in a detached state.
PTHREAD_CREATE_JOINABLE
Threads that are created using attr will be created in a joinable state.
The default setting of the detach state attribute in a newly initialized
threadattributes object is PTHREAD_CREATE_JOINABLE.
The pthread_attr_getdetachstate() returns the detach state attribute of the
threadattributes object attr in the buffer pointed to by detachstate.
线程栈大小
int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize); int pthread_attr_getstacksize(pthread_attr_t *attr, size_t *stacksize);
DESCRIPTION
The pthread_attr_setstacksize() function sets the stack size attribute
of the threadattributes object referred to by attr to the value specified
in stacksize.(一般情况下该值我们设置为0，使用系统默认设置的线程栈大小，否则可能会引起程序的可移植性的问题) The stack size attribute determines the minimum size (in bytes) that will
be allocatedfor threads created using the thread attributes object attr.
The pthread_attr_getstacksize() function returns the stack size attribute of
the threadattributes object referred to by attr in the buffer pointed to by stacksize.
线程栈溢出保护区大小
int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize); int pthread_attr_getguardsize(pthread_attr_t *attr, size_t *guardsize);
线程竞争范围(进程范围内的竞争 or 系统范围内的竞争)
int pthread_attr_getscope(const pthread_attr_t *attr,int *contentionscope); int pthread_attr_setscope(pthread_attr_t *attr, int contentionscope);
contentionscope说明：
PTHREAD_SCOPE_SYSTEM
The thread competes for resources with all other threads in all processes on
the system that are in the same scheduling allocation domain (a group of one or more processors).
PTHREAD_SCOPE_SYSTEM threads are scheduled relative to one anotheraccording to their
scheduling policy and priority.
PTHREAD_SCOPE_PROCESS
The thread competes for resources with all other threads in the same process thatwere
also created with the PTHREAD_SCOPE_PROCESS contention scope.
PTHREAD_SCOPE_PROCESS threads are scheduled relative to other threads in the process
according to their scheduling policy and priority. POSIX.1-2001 leaves it unspecified how these threads contend with other threads in other process
on the system or with other threads in the same process that were created with the
PTHREAD_SCOPE_SYSTEM contention scope.
线程调度策略
int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy); int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);
DESCRIPTION
The pthread_attr_setschedpolicy() function sets the scheduling policy attribute of the thread
attributes object referred to by attr to the value specified in policy. This attribute determines
the scheduling policy of a thread created using the thread attributes object attr.
The supported values for policy are SCHED_FIFO, SCHED_RR, and SCHED_OTHER, as below:
SCHED_FIFO a first-in, first-out policy(先进先出调度策略);
SCHED_RR a round-robin policy(时间片轮转调度算法);
SCHED_OTHER the standard round-robin time-sharing policy(线程一旦开始运行，直到被抢占或者直到线程阻塞或停止为止);
注意:
In order for the policy setting made by pthread_attr_setschedpolicy()
to have effect when calling pthread_create(3), the caller must use pthread_attr_setinheritsched(3)(见下)
to set the inherit-scheduler attribute of the attributes object attr to PTHREAD_EXPLICIT_SCHED(新创建的进程继承自己的调度属性).
线程继承的调度策略
int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inheritsched); int pthread_attr_setinheritsched(pthread_attr_t *attr, int inheritsched);
The following values may be specified in inheritsched:
PTHREAD_INHERIT_SCHED(继承调度属性)
Threads that are created using attr inherit scheduling attributes from the
creating thread; the scheduling attributes in attr are ignored.
PTHREAD_EXPLICIT_SCHED(指定自己的调度属性)
Threads that are created using attr take their scheduling attributes from
the values specified by the attributes object.
The default setting of the inherit-scheduler attribute in a newly initialized thread attributes object is PTHREAD_INHERIT_SCHED.
线程调度参数(实际上我们一般只关心一个参数：线程的优先级,默认为0)
int pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param); int pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param);
//sched_param结构体
struct sched_param {
int sched_priority; /* Scheduling priority */
};
线程的并发级别
int pthread_setconcurrency(int new_level); int pthread_getconcurrency(void);
说明：并发级别仅在N:M线程模型中有效，设置并发级别，给内核一个提示：表示提供给定级别数量的核心线程来映射用户线程是高效的(仅仅是一个提示)，默认为0, 内核按照默认的方式进行并发；
/** 查看线程默认属性 **/
void printThreadAttr()
{
pthread_attr_t attr;
pthread_attr_init(&attr);
int detachstate;
pthread_attr_getdetachstate(&attr, &detachstate);
cout << "detach-state: "
<< (detachstate == PTHREAD_CREATE_JOINABLE ?
"PTHREAD_CREATE_JOINABLE" : "PTHREAD_CREATE_DETACHED")
<< endl;
size_t size;
pthread_attr_getstacksize(&attr, &size);
cout << "stack-size: " << size << endl;
pthread_attr_getguardsize(&attr, &size);
cout << "guard-size: " << size << endl;
int scope;
pthread_attr_getscope(&attr, &scope);
cout << "scope: "
<< (scope == PTHREAD_SCOPE_SYSTEM ?
"PTHREAD_SCOPE_SYSTEM" : "PTHREAD_SCOPE_PROCESS")
<< endl;
int policy;
pthread_attr_getschedpolicy(&attr, &policy);
cout << "policy: ";
switch (policy)
{
case SCHED_FIFO:
cout << "SCHED_FIFO";
break;
case SCHED_RR:
cout << "SCHED_RR";
break;
case SCHED_OTHER:
cout << "SCHED_OTHER";
break;
default:
break;
}
cout << endl;
int inheritsched;
pthread_attr_getinheritsched(&attr, &inheritsched);
cout << "inheritsched: "
<< (inheritsched == PTHREAD_INHERIT_SCHED ?
"PTHREAD_INHERIT_SCHED" : "PTHREAD_INHERIT_SCHED")
<< endl;
struct sched_param param;
pthread_attr_getschedparam(&attr, ¶m);
cout << "scheduling priority: " << param.sched_priority << endl;
cout << "concurrency: " << pthread_getconcurrency() << endl;
pthread_attr_destroy(&attr);
}
说明:
绑定属性:
Linux中采用“一对一”的线程机制，也就是一个用户线程对应一个内核线程。绑定属性就是指一个用户线程固定地分配给一个内核线程，因为CPU时间片的调度是面向内核线程（也就是轻量级进程）的，因此具有绑定属性的线程可以保证在需要的时候总有一个内核线程与之对应。而与之对应的非绑定属性就是指用户线程和内核线程的关系不是始终固定的，而是由系统来控制分配的。
分离属性:
分离属性是用来决定一个线程以什么样的方式来终止自己。在非分离情况下，当一个线程结束时，它所占用的系统资源并没有被释放，也就是没有真正的终止。只有当pthread_join()函数返回时，创建的线程才能释放自己占用的系统资源。而在分离属性情况下，一个线程结束时立即释放它所占有的系统资源。这里要注意的一点是，如果设置一个线程的分离属性，而这个线程运行又非常快，那么它很可能在pthread_create()函数返回之前就终止了，它终止以后就可能将线程号和系统资源移交给其他的线程使用。
