Date: Mon, 10 Sep 2007 00:04:45 +0200 From: Martin Tournoij <carpetsmoker@xs4all.nl> To: freebsd-questions@freebsd.org Subject: Re: Getting the CPU frequency in C Message-ID: <20070909220445.GA40462@glitch.rwxrwxrwx.net> In-Reply-To: <20070909205759.GA35519@owl.midgard.homeip.net> References: <20070909205025.GA40102@glitch.rwxrwxrwx.net> <20070909205759.GA35519@owl.midgard.homeip.net>
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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.
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