Linux下几种加锁方法的比较
在linux2.6.20内核下， 分别执行1000000次的加锁解锁操作， 记录锁： real 0m3.280s user 0m1.943s sys 0m1.216s 信号量锁 real 0m31.255s user 0m8.996s sys 0m21.111s pthread_mutex_t real 0m0.018s user 0m0.015s sys 0m0.003s 与stevens在APUE里记述的结果恰好相反。 源代码如下：
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#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
void test_filelock(int locktimes)
{
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
struct flock lock, unlock;
int count = 0;
int fd;
lock.l_type = F_WRLCK;
lock.l_start = 0;
lock.l_whence = SEEK_SET;
lock.l_len = 1;
unlock.l_type = F_ULOCK;
unlock.l_start = 0;
unlock.l_whence = SEEK_SET;
unlock.l_len = 1;
fd = open("lock.test", O_CREAT);
for (count = 0; count < locktimes; ++count){
fcntl(fd, F_SETLKW, &lock);
fcntl(fd, F_SETLKW, &unlock);
}
}
void test_pthread_lock(int locktimes)
{
int i;
for (i = 0; i < locktimes; ++i){
pthread_mutex_lock(&mutex);
pthread_mutex_unlock(&mutex);
}
}
void test_semlock(int locktimes)
{
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdio.h>
struct sembuf bufLock, bufUnlock;
int iCount = 0;
int semid = semget(0x33332222, 1, IPC_CREAT|0666);
if (semid == -1){
printf("semget error/n");
return ;
}
semctl(semid, 0, SETVAL, 1);
bufLock.sem_num = 0;
bufLock.sem_op = -1;
bufLock.sem_flg = SEM_UNDO;
bufUnlock.sem_num = 0;
bufUnlock.sem_op = 1;
bufUnlock.sem_flg = SEM_UNDO;
for ( iCount = 0; iCount < 10000000; ++iCount){
semop(semid, &bufLock, 1);
semop(semid, &bufUnlock, 1);
}
}
int main(int argc, char **argv)
{
if(argc != 3){
printf("usage: test_lock file|sem|pthread locktimes/n");
exit(1);
}
int locktimes = atoi(argv[2]);
if(strcmp(argv[1], "file") == 0)
test_filelock(locktimes);
else if(strcmp(argv[1], "sem") == 0)
test_semlock(locktimes);
else
test_pthread_lock(locktimes);
return 0;
}
另外，如果只需要一把锁的话，flock使用更方便，效率上于记录锁基本相同