TCP并发服务器(七)——可动态增减的线程池，主线程accept——基于UNP代码修改
1.说明
线程池基于一个区间动态变化，在客户连接过多线程不够用时，动态增加一定数量的线程。在线程闲置数量多于一半时，动态减小线程数量到一个基准线。
这个例子模式为：半同步/半异步（half-sync/half-async）
2.代码相关说明
代码基于UNP的库函数，要想运行必须先安装相应库。
3.代码
若是不可动态增加的线程池版本版本慢于上节的版本。
原因在于多用了条件变量。
在主线程调用pthread_cond_signal引起线程函数库基于条件变量执行唤醒时，该函数库在所有可用线程中轮循唤醒一个。
#include "unpthread.h" #include <queue> #include <list> #include <vector> using std::vector; using std::list; using std::queue; //可以将下面的信息放入一个结构体中，作为线程池结构 const int MAX_NTHREADS = 30; //线程池能够创建的最大线程数 const int MIN_NTHREADS = 15; //线程池中最小线程数 const int MINFREE_NTHREADS = 2; //允许的最小空闲线程数 const int ADD_NTHREADS = 5; //空闲线程数< MINFREE_NTHREDS时增加的线程数 //记录每个线程信息 typedef struct { bool thread_flag; //是否正在记录线程信息；true: 是； false: 否 pthread_t thread_tid; //线程的ID号 long thread_count; //此线程被执行的次数 } thread_info; static thread_info thread_info_array[MAX_NTHREADS]; //存放所有的线程信息 static int total_nthreads = MIN_NTHREADS; //当前存在的总线程数,初始化线程池的大小 static int free_nthreads = MIN_NTHREADS; //空闲的线程数量 //static queue<int> clifd_list; static list<int> clifd_list; //已连接的客户端描述符队列 //static forward_list<int> clifd_list; //const int MAXNCLI = 50; //UNP中的最大的客户端数目 //static int clifd[MAXNCLI], iget, iput; //循环队列： UNP中用于存放已连接的客户，和取放客户端的位置。可以使用vector做循环队列在不够时动态增加长度。 static pthread_mutex_t clifd_mutex = PTHREAD_MUTEX_INITIALIZER; static pthread_cond_t clifd_cond = PTHREAD_COND_INITIALIZER; static void sig_int(int signo) { void pr_cpu_time(void); pr_cpu_time(); exit(0); } //线程运行函数 void *thread_main(void *arg) { //arg是在thread_info_array中的位置 int thread_pos = (int)arg; DPRINTF("thread %d starting ", thread_pos); void web_child(int); for (;;) { DPRINTF("thread %d, threadID %d want to lock ", thread_pos, thread_info_array[thread_pos].thread_tid); //给当前的线程上锁 Pthread_mutex_lock(&clifd_mutex); DPRINTF("thread %d threadID %d, thread_id %d locked ", thread_pos, thread_info_array[thread_pos].thread_tid, pthread_self()); //UNP中原本的循环数组 /* while (iget == iput) { DPRINTF("no jobs, thread %d wait cond "); Pthread_cond_wait(&clifd_cond, &clifd_mutex); DPRINTF("thread %d wait signal cond ", thread_pos); } int connfd = clifd[iget]; if (++iget == MAXNCLI) { iget = 0; } */ //没有已连接的客户 while (clifd_list.empty()) { //busy_nthreads = 0; //memset(thread_busyflag, 0, MAX_NTHREADS); //free_nthreads = total_nthreads; DPRINTF("no jobs, thread %d wait cond "); //等待条件变量，此时mutex解锁。 //被唤醒后，重新加锁 Pthread_cond_wait(&clifd_cond, &clifd_mutex); DPRINTF("thread %d wait signal cond ", thread_pos); } //for (int i = 0; i < MAX_NTHREADS; ++i) { // if (thread_info_list[i].thread_busyflag == 0) { // ++free_nthreads; // } //} //空线程数目 free_nthreads = total_nthreads - clifd_list.size(); //当前线程不够用 if (free_nthreads < 0) { free_nthreads = 0; } //空闲线程数超过一半 if (free_nthreads > total_nthreads / 2 && total_nthreads > MIN_NTHREADS) { DPRINTF("*free %d, total %d**********************************Free a thread ", free_nthreads, total_nthreads); //减小线程数目 --total_nthreads; //标识此结构没有再用 thread_info_array[thread_pos].thread_flag = false; //分离当前线程，线程结束系统回收资源 Pthread_detach(pthread_self()); //thread_info_list[thread_pos].thread_busyflag = 0; //解锁互斥量 Pthread_mutex_unlock(&clifd_mutex); //线程退出 pthread_exit(NULL); } int connfd = clifd_list.front(); //clifd_list.pop(); clifd_list.pop_front(); //++busy_nthreads; //--free_nthreads; //thread_busyflag[thread_pos] = true; //thread_info_list[thread_pos].thread_busyflag = 1; Pthread_mutex_unlock(&clifd_mutex); DPRINTF("thread %d unlocked ", thread_pos); //++thread_info_list[thread_pos].thread_count;
//执行相应任务 web_child(connfd); Close(connfd); //thread_busyflag[thread_pos] = false; } } //创建线程，记录线程信息：ID，结构是否在用 void thread_make(int i) { Pthread_create(&thread_info_array[i].thread_tid, NULL, &thread_main, (void*)i); thread_info_array[i].thread_flag = true; return; } int main(int argc, char *argv[]) { socklen_t addrlen; int listenfd; if (argc == 3) { //IP:Port listenfd = Tcp_listen(NULL, argv[1], &addrlen); } else if (argc == 4) { //用于指定ipv4还是ipv6 listenfd = Tcp_listen(argv[1], argv[2], &addrlen); } else { err_quit("Usage: a.out [ <host> ] <port#> <#threads>"); } struct sockaddr *cliaddr = (struct sockaddr*)Malloc(addrlen); // total_nthreads = atoi(argv[argc - 1]); //thread_info_list = (Thread*)Calloc(total_nthreads, sizeof(Thread)); //iget = iput = 0; //create all threads,开始数目是线程池允许的最小数目 for (int i = 0; i < total_nthreads; ++i) { thread_make(i); } //中断用于比较时间 Signal(SIGINT, sig_int); for (;;) { DPRINTF("Busy thread number is %d ", clifd_list.size()); DPRINTF("Free thread number is %d ", free_nthreads); DPRINTF("Total thread number is %d ", total_nthreads); socklen_t clilen = addrlen; DPRINTF("Wait for a connection "); //获取已连接的描述符 int connfd = Accept(listenfd, cliaddr, &clilen); DPRINTF("Accept a connection "); DPRINTF("Main thread want to lock "); //加锁更改存放描述符的结构 Pthread_mutex_lock(&clifd_mutex); DPRINTF("Main thread locked "); /*clifd[iput] = connfd; if (++iput == MAXNCLI) { iput = 0; } if (iput == iget) { err_quit("iput = iget = %d ", iput); }*/ //clifd_list.push(connfd); clifd_list.push_back(connfd); //空闲线程数 free_nthreads = total_nthreads - clifd_list.size(); if (free_nthreads < 0) { free_nthreads = 0; } //空闲连接数小于允许的最小空闲连接数目，增加线程数木 if (free_nthreads < MINFREE_NTHREADS && total_nthreads < MAX_NTHREADS) { for (int i = 0; i < ADD_NTHREADS; ++i, ++total_nthreads) { DPRINTF("******************************create a new threads "); for (int j = 0; j < MAX_NTHREADS; ++j) { if (thread_info_array[j].thread_flag == false) { thread_make(j); } } } } //广播条件变量，唤醒正在等待的线程 Pthread_cond_signal(&clifd_cond); DPRINTF("Main thread singal cond "); Pthread_mutex_unlock(&clifd_mutex); DPRINTF("Main thread unlocked "); } return 0; }