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 88CE6C4338F for ; Thu, 5 Aug 2021 05:32:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C75A36052B for ; Thu, 5 Aug 2021 05:32:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C75A36052B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 0F2896B006C; Thu, 5 Aug 2021 01:32:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0A3526B0071; Thu, 5 Aug 2021 01:32:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ED37B8D0001; Thu, 5 Aug 2021 01:32:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0006.hostedemail.com [216.40.44.6]) by kanga.kvack.org (Postfix) with ESMTP id D4B756B006C for ; Thu, 5 Aug 2021 01:32:22 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 6A7568249980 for ; Thu, 5 Aug 2021 05:32:22 +0000 (UTC) X-FDA: 78439906524.22.2FEA81B Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by imf13.hostedemail.com (Postfix) with ESMTP id 98D81100EC28 for ; Thu, 5 Aug 2021 05:32:21 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10066"; a="214104177" X-IronPort-AV: E=Sophos;i="5.84,296,1620716400"; d="scan'208";a="214104177" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 22:32:18 -0700 X-IronPort-AV: E=Sophos;i="5.84,296,1620716400"; d="scan'208";a="522386543" Received: from gao-cwp.sh.intel.com (HELO gao-cwp) ([10.239.159.133]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 22:32:14 -0700 Date: Thu, 5 Aug 2021 13:39:40 +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: <20210805053938.GA12593@gao-cwp> References: <20210522160827.GA2625834@paulmck-ThinkPad-P17-Gen-1> <20210526064922.GD5262@shbuild999.sh.intel.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210805040349.GD4397@paulmck-ThinkPad-P17-Gen-1> User-Agent: Mutt/1.9.4 (2018-02-28) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 98D81100EC28 Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf13.hostedemail.com: domain of chao.gao@intel.com has no SPF policy when checking 134.134.136.65) smtp.mailfrom=chao.gao@intel.com X-Stat-Signature: ke3dihzu6bierhiegrie1xpyx8u39fwf X-HE-Tag: 1628141541-448755 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [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 > >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. > >My current thought is that if more than (say) 100 consecutive attempts >to read the clocksource get hit with excessive delays, it is time to at >least do a WARN_ON(), and maybe also time to disable the clocksource >due to skew. The reason is that if reading the clocksource -always- >sees excessive delays, perhaps the clock driver or hardware is to blame. > >Thoughts? It makes sense to me. Thanks Chao