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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 720FFC47254 for ; Sat, 2 May 2020 14:26:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A49021835 for ; Sat, 2 May 2020 14:26:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728109AbgEBO02 (ORCPT ); Sat, 2 May 2020 10:26:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:34224 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728020AbgEBO02 (ORCPT ); Sat, 2 May 2020 10:26:28 -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 D010BB019; Sat, 2 May 2020 14:26:26 +0000 (UTC) Message-ID: <1588429584.8505.31.camel@suse.cz> Subject: Re: [PATCH 2/2] x86, sched: Bail out of frequency invariance if turbo frequency is unknown From: Giovanni Gherdovich To: Peter Zijlstra Cc: Srinivas Pandruvada , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Len Brown , "Rafael J . Wysocki" , x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Ricardo Neri , Linus Torvalds Date: Sat, 02 May 2020 16:26:24 +0200 In-Reply-To: <20200501130427.GD3762@hirez.programming.kicks-ass.net> References: <20200428132450.24901-1-ggherdovich@suse.cz> <20200428132450.24901-3-ggherdovich@suse.cz> <20200501130427.GD3762@hirez.programming.kicks-ass.net> 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 Fri, 2020-05-01 at 15:04 +0200, Peter Zijlstra wrote: > On Tue, Apr 28, 2020 at 03:24:50PM +0200, Giovanni Gherdovich wrote: > > There may be CPUs that support turbo boost but don't declare any turbo > > ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition > > scale-invariant calculations can't be performed. > > > > Signed-off-by: Giovanni Gherdovich > > Suggested-by: Ricardo Neri > > Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance") > > --- > > arch/x86/kernel/smpboot.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > > index 4718f29a3065..ab2a0df7d1fb 100644 > > --- a/arch/x86/kernel/smpboot.c > > +++ b/arch/x86/kernel/smpboot.c > > @@ -1991,9 +1991,11 @@ static bool intel_set_max_freq_ratio(void) > > /* > > * Some hypervisors advertise X86_FEATURE_APERFMPERF > > * but then fill all MSR's with zeroes. > > + * Some CPUs have turbo boost but don't declare any turbo ratio > > + * in MSR_TURBO_RATIO_LIMIT. > > */ > > - if (!base_freq) { > > - pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n"); > > + if (!base_freq || !turbo_freq) { > > + pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n"); > > return false; > > } > > I've added the below, imagine base_freq > turbo_freq * > SCHED_CAPACITY_SCALE. Right, I didn't consider that case. It doesn't hurt to be defensive. I understand you've already edited the patches in your tree, so I am not resending, just confirming my Signed-off-by: Giovanni Gherdovich > > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1975,6 +1975,7 @@ static bool core_set_max_freq_ratio(u64 > static bool intel_set_max_freq_ratio(void) > { > u64 base_freq, turbo_freq; > + u64 turbo_ratio; > > if (slv_set_max_freq_ratio(&base_freq, &turbo_freq)) > goto out; > @@ -2008,9 +2009,15 @@ static bool intel_set_max_freq_ratio(voi > return false; > } > > - arch_turbo_freq_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE, > - base_freq); > + turbo_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE, base_freq); > + if (!turbo_ratio) { > + pr_debug("Non-zero turbo and base frequencies led to a 0 ratio.\n"); > + return false; > + } > + > + arch_turbo_freq_ratio = turbo_ratio; > arch_set_max_freq_ratio(turbo_disabled()); > + > return true; > } >