Linux sysconf(_SC_CLK_TCK) 它返回什么？
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sysconf(_SC_CLK_TCK) what does it return?
提问by liv2hak
I was trying to understand various sysconf macros.I have written a program as below.
我试图理解各种 sysconf 宏。我编写了一个程序，如下所示。
int main()
{
fprintf(stdout, "No. of clock ticks per sec : %ld\n",sysconf(_SC_CLK_TCK));
return 0;
}
I always get the result as 100.I am running it on a CPU that is clocked at 2.93GHz.What does the number 100 exactly mean.?
我总是得到 100 的结果。我在主频为 2.93GHz 的 CPU 上运行它。数字 100 到底是什么意思。？
回答by iabdalkader
It's just the number of clock ticks per second, in your case the kernel is configured for 100 clocks per second (or 100Hz clock).
这只是每秒时钟滴答数，在您的情况下，内核配置为每秒 100 个时钟（或 100Hz 时钟）。
回答by user3163041
The number of clock ticks per second can be found by the sysconf system call,
每秒时钟滴答数可以通过 sysconf 系统调用找到，
printf ("_SC_CLK_TCK = %ld\n", sysconf (_SC_CLK_TCK));
A typical value of clock ticks per second is 100. That is, in this case, there is a clock tick every 10 milliseconds or 0.01 second. To convert the clock_t values, returned by times, into seconds one has to divide by the number of clock ticks per second. An example program using the times and sysconf (_SC_CLK_TCK) system calls is,
每秒时钟滴答的典型值为 100。也就是说，在这种情况下，每 10 毫秒或 0.01 秒就有一个时钟滴答。要将由时间返回的clock_t 值转换为秒，必须除以每秒时钟滴答数。使用时间和 sysconf (_SC_CLK_TCK) 系统调用的示例程序是，
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <sys/times.h>
main ()
{
clock_t ct0, ct1;
struct tms tms0, tms1;
int i;
if ((ct0 = times (&tms0)) == -1)
perror ("times");
printf ("_SC_CLK_TCK = %ld\n", sysconf (_SC_CLK_TCK));
for (i = 0; i < 10000000; i++)
;
if ((ct1 = times (&tms1)) == -1)
perror ("times");
printf ("ct0 = %ld, times: %ld %ld %ld %ld\n", ct0, tms0.tms_utime,
tms0.tms_cutime, tms0.tms_stime, tms0.tms_cstime);
printf ("ct1 = %ld, times: %ld %ld %ld %ld\n", ct1, tms1.tms_utime,
tms1.tms_cutime, tms1.tms_stime, tms1.tms_cstime);
printf ("ct1 - ct0 = %ld\n", ct1 - ct0);
}
Source
来源
http://www.softprayog.in/tutorials/linux-process-execution-time
http://www.softprayog.in/tutorials/linux-process-execution-time
