Test the latency of signal epoll_wait() to return by kill()

epoll_latency.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>
#include <sys/epoll.h>
#include <pthread.h>
#include <signal.h>


double microtime(){
	struct timeval now;
	gettimeofday(&now, NULL);
	double ret = now.tv_sec + now.tv_usec/1000.0/1000.0;
	return ret;
}


#define MAX_EVENTS 10
struct epoll_event ev, events[MAX_EVENTS];
int epollfd;

int signaled = 0;
double sig_time = 0;


void signal_handler(int sig){
//	fprintf(stderr, "%d %.6f signal_handler\n", __LINE__, microtime());
}

void* run_thread(void *arg){
	while(1){
		sleep(1);
		//fprintf(stderr, "%d %.6f signal 1\n", __LINE__, microtime());
		kill(getpid(), SIGALRM);
		signaled = 1;
		sig_time = microtime();
		//fprintf(stderr, "%d %.6f signal 2\n", __LINE__, microtime());
	}
	return (void *)NULL;
}

void init(){
	epollfd = epoll_create(1024);
	if (epollfd == -1) {
		perror("epoll_create");
		exit(EXIT_FAILURE);
	}

	signal(SIGALRM, signal_handler);

	pthread_t tid;
	int err = pthread_create(&tid, NULL, run_thread, NULL);
}

int main(int argc, char **argv){
	init();
	while(1){
		int nfds = epoll_wait(epollfd, events, MAX_EVENTS, 10);
		if(signaled){
			signaled = 0;
			double latency = microtime() - sig_time;
			fprintf(stderr, "%d %.6f latency = %.6f\n", __LINE__, microtime(), latency);
		}
		//fprintf(stderr, "%d %.6f epoll_wait\n", __LINE__, microtime());
		if (nfds == -1) {
			if(errno == EINTR){
				continue;
			}
			perror("epoll_wait");
			exit(EXIT_FAILURE);
		}

	}
	return 0;
}