分类:
2008-11-26 18:05:55
8.16 process times
讲了怎么给一个process计时,这个计时包括:
1. Clock time及程序总共从启动到结束的时间差
2. user time,即在用户层使用的时间
3. system time即,在system层使用的时间。
当然要求在启动时和退出时两个时间点作两次记录,然后两次的结果做减法来得到。
单位都是ticks,一般CPU在一秒钟都有几十个ticks,这个可以通过sysconf获得。
接口:
#include clock_t times(struct tms *buf); |
Returns: elapsed wall clock time in clock ticks if OK, 1 on error |
struct tms {
clock_t tms_utime; /* user CPU time */
clock_t tms_stime; /* system CPU time */
clock_t tms_cutime; /* user CPU time, terminated children */
clock_t tms_cstime; /* system CPU time, terminated children */
};
例子:
#include "apue.h"
#include
static void pr_times(clock_t, struct tms *, struct tms *);
static void do_cmd(char *);
int
main(int argc, char *argv[])
{
int i;
setbuf(stdout, NULL);
for (i = 1; i < argc; i++)
do_cmd(argv[i]); /* once for each command-line arg */
exit(0);
}
static void
do_cmd(char *cmd) /* execute and time the "cmd" */
{
struct tms tmsstart, tmsend;
clock_t start, end;
int status;
printf("\ncommand: %s\n", cmd);
if ((start = times(&tmsstart)) == -1) /* starting values */
err_sys("times error");
if ((status = system(cmd)) < 0) /* execute command */
err_sys("system() error");
if ((end = times(&tmsend)) == -1) /* ending values */
err_sys("times error");
pr_times(end-start, &tmsstart, &tmsend);
pr_exit(status);
}
static void
pr_times(clock_t real, struct tms *tmsstart, struct tms *tmsend)
{
static long clktck = 0;
if (clktck == 0) /* fetch clock ticks per second first time */
if ((clktck = sysconf(_SC_CLK_TCK)) < 0)
err_sys("sysconf error");
printf(" real: %7.2f \n", real / (double) clktck);
printf(" user: %7.2f \n",
(tmsend->tms_utime - tmsstart->tms_utime) / (double) clktck);
printf(" sys: %7.2f \n",
(tmsend->tms_stime - tmsstart->tms_stime) / (double) clktck);
printf(" child user: %7.2f \n",
(tmsend->tms_cutime - tmsstart->tms_cutime) / (double) clktck);
printf(" child sys: %7.2f \n",
(tmsend->tms_cstime - tmsstart->tms_cstime) / (double) clktck);
}
结果:
$ ./a.out "sleep 5" "date"
command: sleep 5
real: 5.02
user: 0.00
sys: 0.00
child user: 0.01
child sys: 0.00
normal termination, exit status = 0
command: date
Mon Mar 22 00:43:58 EST 2004
real: 0.01
user: 0.00
sys: 0.00
child user: 0.01
child sys: 0.00
normal termination, exit status = 0