我编写了一个循环 fork 的程序。子进程唯一要做的就是增加计数器并退出,而父进程等待它们中的每一个。
我的目标是分别测量父进程及其所有子进程的用户和系统时间。 我已经使用 times() 函数和 struct tms 成功完成了父进程。令人惊讶的是,对子进程的相同方法不起作用。我在做什么错误?如何衡量这些时间?
我也试过 getrusage() 但失败了。
我的代码:
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/times.h>
#include <time.h>
#ifndef COUNT
#define COUNT 100000
#endif
int counter;
int main(){
struct tms time1,time2;
times(&time1);
int count = COUNT;
pid_t pid;
while(count--){
if((pid=fork())<0){
printf("fork error\n");
} else if(pid==0){ /* child */
counter++;
_exit(0);
} else {
waitpid(pid,NULL,0); /*wait()*/
}
}
printf("COUNTER: %d\n",counter);
times(&time2);
long double clktck=sysconf(_SC_CLK_TCK);
double user=(time2.tms_utime-time1.tms_utime)/(double)clktck;
double system=(time2.tms_stime-time1.tms_stime)/(double)clktck;
double cuser=(time2.tms_cutime-time1.tms_cutime)/(double)clktck;
double csystem=(time2.tms_cstime-time1.tms_cstime)/(double)clktck;
printf("USER:%lf\nSYSTEM:%lf\n",user,system);
printf("CUSER:%lf\nCSYSTEM:%lf\n",cuser,csystem);
return 0;
}
最佳答案
我认为问题在于您的 child 执行太快;他们没有花足够的时间来执行,所以他们的时间总和是很多零。为了检验这个理论,我稍微修改了你的程序:
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/times.h>
#include <time.h>
#ifndef COUNT
#define COUNT 100
#endif
int counter;
int main(){
struct tms time1,time2;
times(&time1);
int count = COUNT;
pid_t pid;
while(count--){
if((pid=fork())<0){
printf("fork error\n");
} else if(pid==0){ /* child */
int i;
for (i=0; i<10000; i++) {
printf("in child %i\n", getpid());
}
exit(0);
} else {
waitpid(pid,NULL,0); /*wait()*/
}
}
printf("COUNTER: %d\n",counter);
times(&time2);
printf("%lu %lu %lu %lu\n", time2.tms_utime, time2.tms_stime, time2.tms_cutime, time2.tms_cstime);
long double clktck=sysconf(_SC_CLK_TCK);
double user=(time2.tms_utime-time1.tms_utime)/(double)clktck;
double system=(time2.tms_stime-time1.tms_stime)/(double)clktck;
double cuser=(time2.tms_cutime-time1.tms_cutime)/(double)clktck;
double csystem=(time2.tms_cstime-time1.tms_cstime)/(double)clktck;
printf("USER:%lf\nSYSTEM:%lf\n",user,system);
printf("CUSER:%lf\nCSYSTEM:%lf\n",cuser,csystem);
return 0;
}
你会看到我大大减少了 child 的数量,让 children 做一些真正的工作; 10_000
printf(... getpid())
操作。 现在时代已经成为某种东西:
$ time ./times
...
in child 16181
COUNTER: 0
1 0 24 95
USER:0.010000
SYSTEM:0.000000
CUSER:0.240000
CSYSTEM:0.950000
real 0m2.234s
user 0m0.250s
sys 0m0.950s
恐怕您的 child 只是没有足够的工作来成就任何事情。 (奇怪,听起来像是育儿建议。)
关于c - 测量父进程和子进程的时间,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5608984/