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	id 167B26D479; Mon, 10 Sep 2007 00:04:46 +0200 (CEST)
Date: Mon, 10 Sep 2007 00:04:45 +0200
From: Martin Tournoij <carpetsmoker@xs4all.nl>
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Subject: Re: Getting the CPU frequency in C
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On Sun 09 Sep 2007 22:09, Erik Trulsson wrote:
> On Sun, Sep 09, 2007 at 10:50:25PM +0200, Martin Tournoij wrote:
> > I'm trying to get the CPU frequency in C:
> > 
> > #include <unistd.h>
> > #include <time.h>
> > #include <ctype.h>
> > #include <sys/sysctl.h>
> > #include <stdio.h>
> > #include <sys/time.h>
> > 
> > int main()
> > {
> >     int mib[2];
> >     size_t size;
> >     struct clockinfo clockrate;
> > 
> >     mib[0] = CTL_KERN;
> >     mib[1] = KERN_CLOCKRATE;
> >     size = sizeof clockrate;
> >     sysctl(mib, 2, &clockrate, &size, NULL, 0);
> > 
> >     fprintf(stdout, "hz: %i\n", clockrate.hz);
> >     fprintf(stdout, "tick: %i\n", clockrate.tick);
> >     fprintf(stdout, "spare: %i\n", clockrate.spare);
> >     fprintf(stdout, "stathz: %i\n", clockrate.stathz);
> >     fprintf(stdout, "profhz: %i\n", clockrate.profhz);
> > 
> >     return 0;
> > }
> > 
> > I tried to run this on two machines (one machine with hw.clockrate: 1378 and
> > the other 797) and it outputs the same on both:
> > hz: 1000
> > tick: 1000
> > spare: 0
> > stathz: 133
> > profhz: 666
> > 
> > The profhz value suggest the devil is at work :D although it's probably a some
> > stupid mistake on my part :/ Can anyone help?
> 
> None of the kern.clockrate entries has any particular relationship with the
> CPU clock frequency, so it is not unexpected that you would get the same
> output from both machines.
> 
> I think looking at hw.clockrate is the most portable you can get.
> If your CPU is using Cool'n'Quiet or the Intel equivalent you can also
> look at dev.cpu.N.freq for the current frequency.

I got confused because they both have the same name ... do'h

hw.clockrate doesn't seem to available through C(?), exec-ing sysctl
hw.clockrate would work, but that's not very elegant...

dev.cpu.0.freq doesn't seem to exists on my (Athlon) CPU, it
does on my PIII CPU though.