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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E4B79C433ED for ; Fri, 23 Apr 2021 19:14:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A44006144A for ; Fri, 23 Apr 2021 19:14:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243697AbhDWTP2 (ORCPT ); Fri, 23 Apr 2021 15:15:28 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:47894 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231684AbhDWTP1 (ORCPT ); Fri, 23 Apr 2021 15:15:27 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1619205289; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XRRccMIE3B0r4h6fyeNGlYwZXtoJwsJnMvcwiPXdThg=; b=lJOMtXM1WsvXnCU8Gn9mDDN/CbosOsN/69wT8tU5Xl4Wzet8NGUgKLzFk5LfHUgNacWIhm sL1Cy1HxhyPdJk9f1hQXT+aHeRozCrcmLuRGThwZg/XE79beq6Wj1kqW/i/rzLv8WHN3v3 FCuJKLKJxC4gkYHEbJwQqjNierIKHUsdEW0iFysbgU75LB91ZA6W4/LM0HkAroDCpe9CRP 5JzzQPWnOgc8j0wYqNuPy+jAKJj4MtJqO3dAyoOS7jQhHN15gZKEXnjD83MPh9KRmUC5wF fpqHBNCPZd+BmE+8G6h4bBZONjZIPAjrDWlnjLMiR7aIGHGKt8wpoVg4A2y+hw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1619205289; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XRRccMIE3B0r4h6fyeNGlYwZXtoJwsJnMvcwiPXdThg=; b=2CxWF3lgZNEqxPhjv6pK5IQ0EBFXNAFXU9eKGiv6+xCtOEf4FNM4UzW+HeKiheE/ppE8RV +6uLV48T4y3Ot6AQ== To: paulmck@kernel.org, Feng Tang Cc: Xing Zhengjun , John Stultz , Stephen Boyd , Jonathan Corbet , Mark Rutland , Marc Zyngier , Andi Kleen , Chris Mason , LKML , lkp@lists.01.org, lkp@intel.com Subject: Re: [LKP] Re: [clocksource] 6c52b5f3cf: stress-ng.opcode.ops_per_sec -14.4% regression In-Reply-To: <20210422142454.GD975577@paulmck-ThinkPad-P17-Gen-1> References: <20210420064934.GE31773@xsang-OptiPlex-9020> <20210420134331.GM975577@paulmck-ThinkPad-P17-Gen-1> <20210420140552.GA3158164@paulmck-ThinkPad-P17-Gen-1> <04f4752e-6c5a-8439-fe75-6363d212c7b2@intel.com> <20210421134224.GR975577@paulmck-ThinkPad-P17-Gen-1> <20210422074126.GA85095@shbuild999.sh.intel.com> <20210422142454.GD975577@paulmck-ThinkPad-P17-Gen-1> Date: Fri, 23 Apr 2021 21:14:49 +0200 Message-ID: <87tunwvmmu.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 22 2021 at 07:24, Paul E. McKenney wrote: > On Thu, Apr 22, 2021 at 03:41:26PM +0800, Feng Tang wrote: > So what are our options? > > 1. Clear CLOCK_SOURCE_MUST_VERIFY from tsc-early. > > 2. #1, but add tsc-early into the watchdog list and set > CLOCK_SOURCE_MUST_VERIFY once it is better calibrated. > > 3. Add a field to struct clocksource that, if non-zero, gives > the maximum drift in nanoseconds per half second (AKA > WATCHDOG_INTERVAL). If zero, the WATCHDOG_MAX_SKEW value > is used. Set this to (say) 150,000ns for tsc-early. > > 4. As noted earlier, increase WATCHDOG_MAX_SKEW to 150 microseconds, > which again is not a good approach given the real-world needs > of real-world applications. > > 5. Your ideas here. #3 or add a flag to the clocksource which says 'frequency is guesswork' and increase the threshold based on that. If that flag is still set max_drift is != 0 after 20 seconds yell. Thanks, tglx