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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 958A0C83003 for ; Wed, 29 Apr 2020 08:15:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D161206D9 for ; Wed, 29 Apr 2020 08:15:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726635AbgD2IPO (ORCPT ); Wed, 29 Apr 2020 04:15:14 -0400 Received: from mx2.suse.de ([195.135.220.15]:50174 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726355AbgD2IPO (ORCPT ); Wed, 29 Apr 2020 04:15:14 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5DA56AB8F; Wed, 29 Apr 2020 08:15:11 +0000 (UTC) Message-ID: <1588148110.21179.63.camel@suse.cz> Subject: Re: [PATCH] x86: move turbo_disabled() out of intel_set_max_freq_ratio From: Giovanni Gherdovich To: Li RongQing , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com Date: Wed, 29 Apr 2020 10:15:10 +0200 In-Reply-To: <1588125007-8799-1-git-send-email-lirongqing@baidu.com> References: <1588125007-8799-1-git-send-email-lirongqing@baidu.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-04-29 at 09:50 +0800, Li RongQing wrote: > move the turbo_disabled before intel_set_max_freq_ratio, > when turbo is disabled, the max frequency ratio is a const > value, it is unnecessary to read MSR_TURBO_RATIO* msr to > compute > > Signed-off-by: Li RongQing > --- > arch/x86/kernel/smpboot.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index fe3ab9632f3b..8979c459df2f 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1987,7 +1987,7 @@ static bool intel_set_max_freq_ratio(void) > out: > arch_turbo_freq_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE, > base_freq); > - arch_set_max_freq_ratio(turbo_disabled()); > + arch_set_max_freq_ratio(false); > return true; > } > > @@ -2009,6 +2009,9 @@ static void init_freq_invariance(void) > if (smp_processor_id() != 0 || !boot_cpu_has(X86_FEATURE_APERFMPERF)) > return; > > + if (turbo_disabled()) > + return; > + > if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) > ret = intel_set_max_freq_ratio(); > Hello, the problem is that turbo can be enabled/disabled by the firmware at runtime, after the machine has booted. This happens for example with the Dell XPS 13, where turbo gets disabled by the firmware if the machine is disconnected from AC power and runs on battery. The laptop could boot on battery (turbo disabled), then after some time the user connects the AC power supply, turbo gets enabled, and with your patch we wouldn't know what is the turbo_freq/base_freq ratio to do frequency invariance (we skipped reading MSR_TURBO_RATIO_LIMIT at boot because turbo was disabled at that timed). This behavior was requested by reviewers in this thread: https://lore.kernel.org/lkml/1906426.HDqaVa71mF@kreacher/ and implemented with 918229cdd5ab ("x86/intel_pstate: Handle runtime turbo disablement/enablement in frequency invariance"). Thanks, Giovanni Gherdovich