Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758317AbYF0IL3 (ORCPT ); Fri, 27 Jun 2008 04:11:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754018AbYF0ILJ (ORCPT ); Fri, 27 Jun 2008 04:11:09 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:32830 "EHLO gprs189-60.eurotel.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752547AbYF0ILG (ORCPT ); Fri, 27 Jun 2008 04:11:06 -0400 Date: Fri, 27 Jun 2008 10:12:02 +0200 From: Pavel Machek To: Alok Kataria Cc: kernel list , Dan Hecht Subject: Re: [RFC PATCH] x86:Use cpu_khz for loops_per_jiffy calculation Message-ID: <20080627081202.GA26613@elf.ucw.cz> References: <20080604061637.6bab3f67@infradead.org> <1213924953.27983.52.camel@promb-2n-dhcp368.eng.vmware.com> <20080620113922.GG7439@elte.hu> <1213999593.31598.52.camel@promb-2n-dhcp368.eng.vmware.com> <20080624175753.GG5642@ucw.cz> <1214500831.3351.10.camel@promb-2n-dhcp368.eng.vmware.com> <20080626173536.GA16783@elf.ucw.cz> <1214503849.3351.35.camel@promb-2n-dhcp368.eng.vmware.com> <20080626221634.GE18719@elf.ucw.cz> <1214521834.3351.54.camel@promb-2n-dhcp368.eng.vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1214521834.3351.54.camel@promb-2n-dhcp368.eng.vmware.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2083 Lines: 60 Hi! > > > > > AFAIU in calibrate_delay_direct too we measure the amount by which timer > > > > > has ticked until DELAY_CALIBRATION_TICKS amount of jiffies has passed. > > > > > So IMO the code there too assumes that there is one loop per timer > > > > > cycle ? > > > > > > > > On my machine, it reports: > > > > > > > > delay using timer specific routine.. 3661.98 BogoMIPS (lpj=7323971) > > > > ... > > > > Detected 1828.828 MHz processor. > > > > > > > > (/proc/cpuinfo) > > > > model name : Genuine Intel(R) CPU T2400 @ 1.83GHz > > > > ... > > > > cpu MHz : 1000.000 > > > How is it 1000 here ? shouldn't this be 1830.xx > > > > cpufreq effect, I believe. > > > > > > bogomips : 3657.54 > > > > > > > > So you'd break it by setting lpj (aka bogomips) to cpu_khz, right? > > > > > > We are not setting it to cpu_khz but to tsc_khz, i am assuming that in > > > this case tsc_khz will be different than cpu_khz. Can you please mail me > > > the full dmesg log. > > > > Yes, but neither cpu_khz nor tsc_khz will be 3657 bogoMips, right? > > Hi Pavel, > > Thanks for the dmesg. The HZ value that you are using on this system is > 250, right ? > > If you note the calculations > > + lpj = ((u64)tsc_khz * 1000); > > + do_div(lpj, HZ); > > We are dividing by HZ over here. So you are right in saying that tsc_khz > wont be equal to bogoMips but lpj_fine will surely be computed correct > since we do consider the HZ value. Ok. > Please let me know if you still have any doubts. > Or can i safely assume that you will ACK the patch ;-) Well, I'm not expert-enough in this subsystem (nor comfortable enough with your code) to ACK it, sorry. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/