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 37571C43460 for ; Mon, 26 Apr 2021 12:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3DBC611C1 for ; Mon, 26 Apr 2021 12:39:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233576AbhDZMkL (ORCPT ); Mon, 26 Apr 2021 08:40:11 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:33862 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232107AbhDZMkI (ORCPT ); Mon, 26 Apr 2021 08:40:08 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1619440766; 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=mcq1K2/TaL/TqRO/V2iGVJlNefNGUJB7nNGpdtpoe18=; b=hzM2eEmOavfvjWOO0A5z0GeDUfWaODsAGHdC45+dQpcNliyKflPx+WZeuyBiQqMXNpTp99 tD4Skzj++XXVFzIpm3JB9L1sg1yj6lKRlVzXk56yXd+hY4KgT0/4f7UsxPkK3JkhM7TjhC i9hXWsTO7eWueXEmPuDWp2EKiwrjJMr6GemfNGvDGuQ8ZqVxHJco4VVOaiTWAo+2/xlP1z pLXn3K2jAK+vVCXEUMPuiEUOl8kczCWnYGCxrQSjN4q9a2vYbgFS2ZM8+3wHDrkawwhqAh i6ag2YpHL+UR0nmktg51DK5iSklZga5n29w9o//RBA90SC1z4k1zgKe7Cjzm7Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1619440766; 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=mcq1K2/TaL/TqRO/V2iGVJlNefNGUJB7nNGpdtpoe18=; b=e82EtuceKGT+/GVtt3Ppw7wnq9KbyS4amC0ARRdjZqUspURndVwTtZJqEngII+VWNw4NyZ nqmchvXO4MGx0iDQ== To: Feng Tang , "Paul E. McKenney" 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: <20210424122920.GB85095@shbuild999.sh.intel.com> References: <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> <20210422165743.GA162649@paulmck-ThinkPad-P17-Gen-1> <20210423061115.GA62813@shbuild999.sh.intel.com> <20210423140254.GM975577@paulmck-ThinkPad-P17-Gen-1> <20210424122920.GB85095@shbuild999.sh.intel.com> Date: Mon, 26 Apr 2021 14:39:25 +0200 Message-ID: <87pmyhte2q.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 Sat, Apr 24 2021 at 20:29, Feng Tang wrote: > On Fri, Apr 23, 2021 at 07:02:54AM -0700, Paul E. McKenney wrote: > And I'm eager to know if there is any real case of an unreliable tsc > on the 'large numbers' of x86 system which complies with our cpu feature > check. And if there is, my 2/2 definitely should be dropped. Nothing prevents BIOS tinkerers from trying to be 'smart'. My most recent encounter (3 month ago) was on a laptop where TSC drifted off on CPU0 very slowly, but was caught due to the TSC_ADJUST check in idle. I'm still thinking about a solution to avoid that extra timer and the watchdog for these systems, but haven't found anything which I don't hate with a passion yet. Thanks, tglx