From owner-freebsd-questions@FreeBSD.ORG Sun Sep 9 22:47:48 2007 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7554116A417 for ; Sun, 9 Sep 2007 22:47:48 +0000 (UTC) (envelope-from carpetsmoker@rwxrwxrwx.net) Received: from mail.rwxrwxrwx.net (rwxrwxrwx.net [82.93.23.199]) by mx1.freebsd.org (Postfix) with ESMTP id 11A6F13C461 for ; Sun, 9 Sep 2007 22:47:47 +0000 (UTC) (envelope-from carpetsmoker@rwxrwxrwx.net) Received: by mail.rwxrwxrwx.net (Postfix, from userid 1001) id 0EF556D479; Mon, 10 Sep 2007 00:52:08 +0200 (CEST) Date: Mon, 10 Sep 2007 00:52:08 +0200 From: Martin Tournoij To: freebsd-questions@freebsd.org Message-ID: <20070909225208.GA40915@glitch.rwxrwxrwx.net> Mail-Followup-To: freebsd-questions@freebsd.org References: <20070909205025.GA40102@glitch.rwxrwxrwx.net> <20070909205759.GA35519@owl.midgard.homeip.net> <20070909220445.GA40462@glitch.rwxrwxrwx.net> <20070909223203.GA50980@owl.midgard.homeip.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070909223203.GA50980@owl.midgard.homeip.net> User-Agent: mutt-ng/devel-r804 (FreeBSD) Subject: Re: Getting the CPU frequency in C X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 09 Sep 2007 22:47:48 -0000 On Mon 10 Sep 2007 00:09, Erik Trulsson wrote: > On Mon, Sep 10, 2007 at 12:04:45AM +0200, Martin Tournoij wrote: > > 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 > > > > #include > > > > #include > > > > #include > > > > #include > > > > #include > > > > > > > > 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(?), > > Of course it is. Using sysctlbyname(3) to access it works fine: > > #include > #include > #include > > int main() > { > size_t size; > int clockrate; > > size = sizeof clockrate; > sysctlbyname("hw.clockrate", &clockrate, &size, NULL, 0); > > fprintf(stdout, "hz: %i\n", clockrate); > return 0; > } > > > hw.clockrate does however only seem to exist on i386 and amd64 architectures > so if you are running on something else you will have to find some > alternative solution. (Parsing the dmesg(8) output?) > > > > > 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. > > It partly depends on the CPU, and mostly on the BIOS if the cpufreq(4) > kernel module will be activated (assuming it has been loaded in the first > place of course.) Thought you could only fetch the sysctl values defined in sys/sysctl.h with sysctl()/sysctlbyname(), apparently not... Thank you for the help Erik and Mel!