Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757390AbYFZIUu (ORCPT ); Thu, 26 Jun 2008 04:20:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757250AbYFZIT2 (ORCPT ); Thu, 26 Jun 2008 04:19:28 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:2612 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756833AbYFZITV (ORCPT ); Thu, 26 Jun 2008 04:19:21 -0400 Date: Tue, 24 Jun 2008 19:57:53 +0200 From: Pavel Machek To: Alok Kataria Cc: Ingo Molnar , Arjan van de Ven , Thomas Gleixner , LKML , Daniel Hecht , Tim Mann , Zach Amsden , Sahil Rihan Subject: Re: [RFC PATCH] x86:Use cpu_khz for loops_per_jiffy calculation Message-ID: <20080624175753.GG5642@ucw.cz> References: <1212540069.19290.57.camel@promb-2n-dhcp368.eng.vmware.com> <20080603182014.79a38d03@infradead.org> <35f686220806032101h103152dat841818982aaa5052@mail.gmail.com> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1213999593.31598.52.camel@promb-2n-dhcp368.eng.vmware.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1266 Lines: 39 Hi! > On X86 platform we can use the value of tsc_khz computed during tsc calibration > to calculate the loops_per_jiffy value. Its very important to keep the error in > lpj values to minimum as any error in that may result in kernel panic in > check_timer. > In virtualization environment, On a highly overloaded host the guest delay > calibration may sometimes result in errors beyond the ~50% that timer_irq_works > can handle, resulting in the guest panicking. How did you adress 'khz has nothing to do with loops per jiffie' comment? Some cpus can do loop in cycle , some need two cycles, some need half. Pavel > @@ -421,6 +422,10 @@ > return; > } > > + lpj = ((u64)tsc_khz * 1000); > + do_div(lpj, HZ); > + lpj_tsc = lpj; > + > printk("Detected %lu.%03lu MHz processor.\n", > (unsigned long)cpu_khz / 1000, > (unsigned long)cpu_khz % 1000); > -- (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/