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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD403C433F5 for ; Mon, 10 Oct 2022 14:23:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229812AbiJJOXR (ORCPT ); Mon, 10 Oct 2022 10:23:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229691AbiJJOXN (ORCPT ); Mon, 10 Oct 2022 10:23:13 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96DE5719A3 for ; Mon, 10 Oct 2022 07:23:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665411792; x=1696947792; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=MvoKKnOaQzWJzaWake7goHRiYLp5TOmATllrxpn0vjY=; b=nqo8gpJq3Ptpb1tIAwepUU79dXY+FfQyxCkY7RPKP+0w4shjMLWC/GbP +pF4Vk20tuKU4LYvLO52EGI4ogRVO/cO1OgJT+LUGPcs4IeZMlD4KaYDd zqirdh5xoykFgPs05QBFnat2H3NuyzzYoE8fmsin0rCD7rsL31t+lBiLG 1w+jKflqBdMjiMyKhS6XVsnYVaUooycx5hll4JlnI2mTJsjoCYAkDZush IQu7BfH9jmbrMXFO79u7myJdEJF6OK5RrFUFNtpwCRwkP7FPn/h9yipQm 9zkXH1H9DtUFDCrlr3ojygMB4h5yiRAs83RgqHI8bTxXtlmxVqh9Rl1I6 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10496"; a="302974772" X-IronPort-AV: E=Sophos;i="5.95,173,1661842800"; d="scan'208";a="302974772" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2022 07:23:11 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10496"; a="688805855" X-IronPort-AV: E=Sophos;i="5.95,173,1661842800"; d="scan'208";a="688805855" Received: from smajuta-mobl.amr.corp.intel.com (HELO [10.209.115.62]) ([10.209.115.62]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2022 07:23:11 -0700 Message-ID: Date: Mon, 10 Oct 2022 07:23:10 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] x86/tsc: Extend the watchdog check exemption to 4S/8S machine Content-Language: en-US To: Feng Tang , Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, rui.zhang@intel.com, tim.c.chen@intel.com, Xiongfeng Wang , Yu Liao References: <20221009051209.393377-1-feng.tang@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/9/22 18:23, Feng Tang wrote: >>> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c >>> index cafacb2e58cc..b4ea79cb1d1a 100644 >>> --- a/arch/x86/kernel/tsc.c >>> +++ b/arch/x86/kernel/tsc.c >>> @@ -1217,7 +1217,7 @@ static void __init check_system_tsc_reliable(void) >>> if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && >>> boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && >>> boot_cpu_has(X86_FEATURE_TSC_ADJUST) && >>> - nr_online_nodes <= 2) >>> + nr_online_nodes <= 8) >> So you're saying all 8 socket systems since Broadwell (?) are TSC >> sync'ed ? > No, I didn't mean that. I haven't got chance to any 8 sockets > machine, and I got a report last month that on one 8S machine, > the TSC was judged 'unstable' by HPET as watchdog. That's not a great check. Think about numa=fake=4U, for instance. Or a single-socket system with persistent memory and high bandwidth memory. Basically 'nr_online_nodes' is a software construct. It's going to be really hard to infer anything from it about what the _hardware_ is.