Just a sanity check before I sumbit a buig report

Pete French petefrench at ticketswitch.com
Tue Mar 8 06:40:07 PST 2005

The man page for getrusage says that the frequency of the statistics
clock is given by sysconf(_SC_CLK_TCK).

The source code to /usr/bin/time uses a function 'getstathz' to get
the frequency of the statistics clock which is does using sysctl

On my system the first returns 100Hz and the second 128Hz!!!

Now, is this:

1) A bug in /usr/bin/time
2) A bug in sysconf(_SC_CLK_TCK)
3) A bug in the manpage for getrusage
4) A bug in the kernel and the values should not be different
5) A bug in my understanding!

Note that although option '4' is unlikely, if I run the test a.out file
on other FreeBSD systems I get 128 for both values, which is even odder!


Test code (will probably give 128 for both on your system)

#include <stdio.h>
#include <unistd.h>
#include <err.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/sysctl.h>

static int
        struct clockinfo clockrate;
        int mib[2];
        size_t size;

        mib[0] = CTL_KERN;
        mib[1] = KERN_CLOCKRATE;
        size = sizeof clockrate;
        if (sysctl(mib, 2, &clockrate, &size, NULL, 0) == -1)
                err(1, "sysctl kern.clockrate");
        return clockrate.stathz;

        printf("get stat hz = %d\n", getstathz());
        printf("sysconf clock tick = %ld\n", sysconf(_SC_CLK_TCK));
        return 0;

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