信号量与互斥锁性能对比

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/*************************************************************************    > File Name: semaphore.c    > Author: wangzhicheng    > Mail: 2363702560@qq.com     > Created Time: Sun 15 Feb 2015 09:37:23 AM WST ************************************************************************/#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <pthread.h>#include <semaphore.h>#include <sys/types.h>#include <time.h>uint n;pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;sem_t sem_id;time_t start, finish;void *add_unlock(void *arg) {uint i;start = clock();for(i = 0;i < 1e6;i++) n++;finish = clock();return NULL;}void *add_mutex(void *arg) {start = clock();pthread_mutex_lock(&mutex);while(n < 1e6) n++;pthread_mutex_unlock(&mutex);finish = clock();return NULL;}void *add_sem(void *arg) {start = clock();sem_wait(&sem_id);while(n < 1e6) n++;sem_post(&sem_id);finish = clock();return NULL;}int main() {/* * single thread * *///add_unlock(NULL);//double elapse = (double)(finish - start) / CLOCKS_PER_SEC;//printf("elapse time = %lf\n", elapse);   // 0.01s/* * 16 threads synchronize by mutex lock * *//*pthread_t thread_ids[16];int i;for(i = 0;i < 16;i++) {pthread_create(&thread_ids[i], NULL, add_mutex, NULL);}for(i = 0;i < 16;i++) {pthread_join(thread_ids[i], NULL);}double elapse = (double)(finish - start) / CLOCKS_PER_SEC;printf("elapse time = %lf\n", elapse);   // 0.03s*//* * 16 threads synchronize by semaphore * *//*sem_init(&sem_id, 0, 1);pthread_t thread_ids[16];int i;for(i = 0;i < 16;i++) {pthread_create(&thread_ids[i], NULL, add_sem, NULL);}for(i = 0;i < 16;i++) {pthread_join(thread_ids[i], NULL);}double elapse = (double)(finish - start) / CLOCKS_PER_SEC;printf("elapse time = %lf\n", elapse);// 0.016s*/return 0;}
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