From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757412Ab2CESf1 (ORCPT ); Mon, 5 Mar 2012 13:35:27 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:38101 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757082Ab2CESfZ (ORCPT ); Mon, 5 Mar 2012 13:35:25 -0500 Message-ID: <1330972323.2191.74.camel@work-vm> Subject: Re: WARNING: Adjusting tsc more then 11% From: John Stultz To: Dave Jones Cc: Fedora Kernel Team , Linux Kernel , Thomas Gleixner Date: Mon, 05 Mar 2012 10:32:03 -0800 In-Reply-To: <20120305154411.GA29668@redhat.com> References: <20120305154411.GA29668@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12030518-6078-0000-0000-000008BAD716 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2012-03-05 at 10:44 -0500, Dave Jones wrote: > John, > We've had a number of reports the last few weeks triggering > this warning that you added back in October. > > https://bugzilla.redhat.com/show_bug.cgi?id=798600 > https://bugzilla.redhat.com/show_bug.cgi?id=799215 > https://bugzilla.redhat.com/show_bug.cgi?id=799745 > https://bugzilla.redhat.com/show_bug.cgi?id=799872 > > any idea what could have changed to start tripping that up ? > > The reports seem to have started around 3.3-rc4. Huh. No I don't know what would have started causing such a warning. I had expected that there would be some edge hardware that might trip that warning, but I'd expect the noise to start there w/ 3.2 after it was introduced. There's only been spelling & comment changes to the timekeeping core in the 3.3-rc series. Looking at the logs, I'm curious if maybe some of the nohz changes have tweaked us here. If we're hitting longer idle times, it might be possible the ntp error could accumulate to be larger, and then the kernel's frequency adjustments might end up trying to adjust for more then 11%. Its also interesting its only popping up on hardware using the TSC. acpi_pm can only do short idle times, so it wouldn't show up here, but hpet could do reasonably long idles, so I'd think we'd also see some similar hpet warnings. Do you know if this is an occasional thing on any of the affected hardware, or if it happens after every reboot? Are any of the reported boxes systems you have access to in order to reproduce? thanks -john