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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 71743C2D0E4 for ; Mon, 16 Nov 2020 03:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3801922263 for ; Mon, 16 Nov 2020 03:23:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726265AbgKPDWh (ORCPT ); Sun, 15 Nov 2020 22:22:37 -0500 Received: from mga02.intel.com ([134.134.136.20]:59623 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbgKPDWg (ORCPT ); Sun, 15 Nov 2020 22:22:36 -0500 IronPort-SDR: dVvUgWlIefuJFpK1Fgqg0gdbEe0zOxlojTnNNY/X/viOTeyzSxvDW7k5F+DMI7ma119GO/dZqE tvXd9rInwckA== X-IronPort-AV: E=McAfee;i="6000,8403,9806"; a="157720988" X-IronPort-AV: E=Sophos;i="5.77,481,1596524400"; d="scan'208";a="157720988" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Nov 2020 19:22:30 -0800 IronPort-SDR: C+9UVmClgbQXVE9Nm0up9iKW+Io7rYMSXIhKHaP13k8X3o1e/U8LJRu+9DndMKIVxmuyzITj5+ 9l0OKuy62mXw== X-IronPort-AV: E=Sophos;i="5.77,481,1596524400"; d="scan'208";a="543427933" Received: from likexu-mobl1.ccr.corp.intel.com (HELO [10.238.4.107]) ([10.238.4.107]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Nov 2020 19:22:26 -0800 Subject: Re: [PATCH] perf/intel: Remove Perfmon-v4 counter_freezing support To: Peter Zijlstra Cc: Paolo Bonzini , kvm@vger.kernel.org, Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Kan Liang , luwei.kang@intel.com, Thomas Gleixner , wei.w.wang@intel.com, Tony Luck , Stephane Eranian , Mark Gross , Srinivas Pandruvada , linux-kernel@vger.kernel.org References: <20201109021254.79755-1-like.xu@linux.intel.com> <20201110151257.GP2611@hirez.programming.kicks-ass.net> <20201110153721.GQ2651@hirez.programming.kicks-ass.net> From: Like Xu Organization: Intel OTC Message-ID: <11ba9e20-84eb-3ea5-5987-8357ae5af53f@linux.intel.com> Date: Mon, 16 Nov 2020 11:22:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.3 MIME-Version: 1.0 In-Reply-To: <20201110153721.GQ2651@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Peter, On 2020/11/10 23:37, Peter Zijlstra wrote: > -static int __init intel_perf_counter_freezing_setup(char *s) > -{ > - bool res; > - > - if (kstrtobool(s, &res)) > - return -EINVAL; > - > - disable_counter_freezing = !res; > - return 1; > -} > -__setup("perf_v4_pmi=", intel_perf_counter_freezing_setup); ... > Anyway, as it stands I think the whole counter_freezing thing is a > trainwreck and it needs to go. If you really want to drop the counter_freezing stuff, we also need to clean it up in Documentation/admin-guide/kernel-parameters.txt: perf_v4_pmi= [X86,INTEL] Format: Disable Intel PMU counter freezing feature. The feature only exists starting from Arch Perfmon v4 (Skylake and newer). However someone may still need it based on the correct understanding of "Freeze-on-Overflow" as Stephane said. How about renaming and documenting it instead of discarding it completely? Our guest PEBS enabling patches does not completely depend on it and we do not require the administrator to enable perf_v4_pmi for guest PEBS. Would you generously take a look at the perf part in this series? Thanks, Like Xu