From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F555C432BE for ; Fri, 6 Aug 2021 02:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29D55611C8 for ; Fri, 6 Aug 2021 02:02:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230099AbhHFCC4 (ORCPT ); Thu, 5 Aug 2021 22:02:56 -0400 Received: from mga09.intel.com ([134.134.136.24]:31195 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230028AbhHFCCx (ORCPT ); Thu, 5 Aug 2021 22:02:53 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10067"; a="214275346" X-IronPort-AV: E=Sophos;i="5.84,299,1620716400"; d="scan'208";a="214275346" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2021 19:02:38 -0700 X-IronPort-AV: E=Sophos;i="5.84,299,1620716400"; d="scan'208";a="513023514" Received: from gao-cwp.sh.intel.com (HELO gao-cwp) ([10.239.159.133]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2021 19:02:34 -0700 Date: Fri, 6 Aug 2021 10:10:00 +0800 From: Chao Gao To: "Paul E. McKenney" Cc: Feng Tang , kernel test robot , John Stultz , Thomas Gleixner , Stephen Boyd , Jonathan Corbet , Mark Rutland , Marc Zyngier , Andi Kleen , Xing Zhengjun , Chris Mason , LKML , Linux Memory Management List , lkp@lists.01.org, lkp@intel.com, ying.huang@intel.com, zhengjun.xing@intel.com Subject: Re: [clocksource] 8901ecc231: stress-ng.lockbus.ops_per_sec -9.5% regression Message-ID: <20210806020958.GA18104@gao-cwp> References: <20210526134911.GB4441@paulmck-ThinkPad-P17-Gen-1> <20210527182959.GA437082@paulmck-ThinkPad-P17-Gen-1> <20210802062008.GA24720@gao-cwp> <20210802170257.GL4397@paulmck-ThinkPad-P17-Gen-1> <20210803085759.GA31621@gao-cwp> <20210803134816.GO4397@paulmck-ThinkPad-P17-Gen-1> <20210805021646.GA11629@gao-cwp> <20210805040349.GD4397@paulmck-ThinkPad-P17-Gen-1> <20210805053938.GA12593@gao-cwp> <20210805153727.GG4397@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210805153727.GG4397@paulmck-ThinkPad-P17-Gen-1> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 05, 2021 at 08:37:27AM -0700, Paul E. McKenney wrote: >On Thu, Aug 05, 2021 at 01:39:40PM +0800, Chao Gao wrote: >> [snip] >> >> This patch works well; no false-positive (marking TSC unstable) in a >> >> 10hr stress test. >> > >> >Very good, thank you! May I add your Tested-by? >> >> sure. >> Tested-by: Chao Gao > >Very good, thank you! I will apply this on the next rebase. > >> >I expect that I will need to modify the patch a bit more to check for >> >a system where it is -never- able to get a good fine-grained read from >> >the clock. >> >> Agreed. >> >> >And it might be that your test run ended up in that state. >> >> Not that case judging from kernel logs. Coarse-grained check happened 6475 >> times in 43k seconds (by grep "coarse-grained skew check" in kernel logs). >> So, still many checks were fine-grained. > >Whew! ;-) > >So about once per 13 clocksource watchdog checks. > >To Andi's point, do you have enough information in your console log to >work out the longest run of course-grained clocksource checks? Yes. 5 consecutive course-grained clocksource checks. Note that considering the reinitialization after course-grained check, in my calculation, two course-grained checks are considered consecutive if they happens in 1s(+/- 0.3s). Thanks Chao