Hello,
I read this thread :
http://article.gmane.org/gmane.linux.kernel.kernelnewbies/31239 and
have a question about it that I hope somebody will answer :)
1) What exactly does it mean to say that "User space sees value x for
HZ?" I mean, for kernel space, I can understand that if I do things
like nanosleep() etc then the resolution with which I can sleep is
determined by the value of HZ inside the kernel. (or so I think). But
what does the value of HZ in user space mean?
2) I tried the following program at the end of the above message I get
the following values :
#include <unistd.h>
#include <time.h>
#include <stdio.h>
int main()
{
struct timespec res;
double resolution;
printf("UserHZ %ld\n", sysconf(_SC_CLK_TCK));
clock_getres(CLOCK_REALTIME, &res);
resolution = res.tv_sec + (((double)res.tv_nsec)/1.0e9);
printf("SystemHZ %ld\n", (unsigned long)(1/resolution + 0.5));
return 0;
}
I get the values:
UserHZ 100
SystemHZ 1000000000
This looks a bit too high to me?
(My kernel version is 2.6.27/fedora core 10 , /usr/include/asm/param.h
says that HZ is 100 )
Thanks a lot in advance :)
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Primate evolution is the ultimate revenge of the nerds.
(How the mind works, Steven Pinker)
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