3

exp1/task66.c

@@ -0,0 +1,80 @@
+/*
+任务6（任选）：测量和比较fork、pthread_create函数调用所需的执行时间，并进行解释。
+可以多次反复调用读写函数，计算累积时间。
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <sys/time.h>
+#include <sys/wait.h>
+
+#define ITERATIONS 1000
+
+double get_time()
+{
+    struct timeval tv;
+    gettimeofday(&tv, NULL);
+    return tv.tv_sec + tv.tv_usec / 1000000.0;
+}
+
+void *dummy_thread(void *arg)
+{
+    return NULL;
+}
+
+double measure_fork_create()
+{
+    double t_start = get_time();
+    for (int i = 0; i < ITERATIONS; i++)
+    {
+        pid_t pid = fork();
+        if (pid < 0)
+        {
+            perror("fork");
+            exit(1);
+        }
+        if (pid == 0)
+        {
+            /* 子进程立即退出 */
+            _exit(0);
+        }
+        else
+        {
+            /* 父进程等待子进程结束 */
+            waitpid(pid, NULL, 0);
+        }
+    }
+    double t_end = get_time();
+    return (t_end - t_start) / ITERATIONS;
+}
+
+double measure_pthread_create()
+{
+    pthread_t tid;
+    double t_start = get_time();
+    for (int i = 0; i < ITERATIONS; i++)
+    {
+        pthread_create(&tid, NULL, dummy_thread, NULL);
+        pthread_join(tid, NULL);
+    }
+    double t_end = get_time();
+    return (t_end - t_start) / ITERATIONS;
+}
+
+int main()
+{
+    printf("Measuring fork() and pthread_create() overhead...\n");
+    printf("Iterations per test: %d\n\n", ITERATIONS);
+
+    double avg_pthread_time = measure_pthread_create();
+    printf("Average pthread_create() + pthread_join() time: %.6f ms\n",
+           avg_pthread_time * 1000);
+
+    double avg_fork_time = measure_fork_create();
+    printf("Average fork() + waitpid() time:           %.6f ms\n",
+           avg_fork_time * 1000);
+
+    return 0;
+}