Very Computer

Is there a system call that accurately returns CPU frequency?
Or is a do-it-yourself method the only option?

thanks
mh

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Quote:>Is there a system call that accurately returns CPU frequency?
>Or is a do-it-yourself method the only option?

Interesting that you should ask that, because right now
one of the highlighted articles at http://www.veryComputer.com/
is called "How to read CPU speed kstat information from a
program".  It shows how to do just that.

I think http://www.veryComputer.com/
will work as a direct link to the article.

  - Logan
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"Everybody
 Loves to see              
 Justice done
 On somebody else"     ( Bruce*burn, "Justice", 1981 )

The problem you'll encounter is that there isn't just one CPU frequency;
on a multi-cpu system, the OS assumes that CPUs could have different
speeds.

You probably already know that there is a command to do so: 'psrinfo
-v'.  psrinfo uses the kstat framework to figure this information out.
But psrinfo is pretty opaque.  In Solaris 8 and later you can explore
kstats using the kstat(1M) command (which is actually a perl script you
can examine):

$ kstat -p 'cpu_info:::clock_MHz'
cpu_info:8:cpu_info8:clock_MHz          750
cpu_info:9:cpu_info9:clock_MHz          750
cpu_info:10:cpu_info10:clock_MHz        750
cpu_info:11:cpu_info11:clock_MHz        750
cpu_info:16:cpu_info16:clock_MHz        750
cpu_info:17:cpu_info17:clock_MHz        750
cpu_info:18:cpu_info18:clock_MHz        750
cpu_info:19:cpu_info19:clock_MHz        750

This helps you to find out the names of the kstats you are seeking; the
next step is to take a look at the kstat man pages.  See especially
kstat_lookup(), kstat_open(), kstat_read() and friends.  Something like
this works for me:

$ cat > speeds.c
#include <unistd.h>
#include <kstat.h>

int
main(void)
{
        kstat_ctl_t *kc;
        kstat_t *kstatp;
        kstat_named_t *namedp;

        if ((kc = kstat_open()) == NULL) {
                exit(1);
        }

        /*
         * Walk the kstat chain; find those whose module name is cpu_info.
         * Read those kstats in, and look up clock_MHz in each one to find
         * the CPU speed of each CPU on the system.
         */
        for (kstatp = kc->kc_chain; kstatp != NULL; kstatp = kstatp->ks_next) {
                if (strcmp(kstatp->ks_module, "cpu_info") == 0) {
                        int cpu = kstatp->ks_instance;

                        if (kstat_read(kc, kstatp, NULL) == -1)
                                exit(1);

                        namedp = (kstat_named_t *)kstat_data_lookup(kstatp,
                            "clock_MHz");
                        printf("cpu %d: %d MHz\n", cpu, namedp->value.l);
                }
        }

Quote:}

^D

$ cc -o speeds speeds.c -lkstat
$ ./speeds
cpu 8: 750 MHz
cpu 9: 750 MHz
cpu 10: 750 MHz
cpu 11: 750 MHz
cpu 16: 750 MHz
cpu 17: 750 MHz
cpu 18: 750 MHz
cpu 19: 750 MHz

        -dp

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included here are not gospel and may be fiction rather than truth.