Hello RT-users!
I am observing strange behaviour regarding CONFIG_HZ on various
machines, while trying to adjust the tickrate of some systems. I found,
that adjtimex(2) is not behaving the way it should. If I write a simple
program like this:
#include <stdio.h>
#include <sys/timex.h>
int main() {
struct timex t;
adjtimex(&t);
printf("%ld\n",t.tick);
}
, which simply is to print the time in usec between two kernel ticks,
the output makes no sense. On a RT-System with CONFIG_HZ=1000, the
output is "10000" and on a non-RT system with CONFIG_HZ=250 (my
desktop-laptop), the output is "9999" - almost the same.
If I calculate correctly, it should be 1000 with CONFIG_HZ and 4000 with
CONFIG_HZ=250.
Am i wrong, or is this an error?
Btw: adjtimex with a tick of of 1000 gives me this:
root@ap:/tmp# adjtimex --tick 1000
adjtimex: Invalid argument
for this kernel:
USER_HZ = 100 (nominally 100 ticks per second)
9000 <= tick <= 11000
-32768000 <= frequency <= 32768000
on the RT-system with CONFIG_HZ=1000. This is also odd - it should print
"USER_HZ=1000" and not "USER_HZ=100".
Strange... Any ideas?
Best regards,
Dennis
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