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 744ECC54EBE for ; Mon, 16 Jan 2023 09:30:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232477AbjAPJ36 (ORCPT ); Mon, 16 Jan 2023 04:29:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54158 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232702AbjAPJ2z (ORCPT ); Mon, 16 Jan 2023 04:28:55 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEB0A16AC4; Mon, 16 Jan 2023 01:28:53 -0800 (PST) Date: Mon, 16 Jan 2023 09:28:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1673861332; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=G5OPga9s9el+CHbJ947Z6+l1jBqfCaiyuLxg70TImQI=; b=mXgF/mdvSH/Q6YlDNvzjgbl5+BUz48NBSFltjq16o4dE9A5N909n/tT6vuxMCodrmPhiyA PFLopFJ6OY/j1jBDiXYJZG0zUxXgOZq0rsdnkk+ftZ+8JSZkbqFZZ4sOkdK6UprtxmbYgZ +F9S9e/fj9/fbTE4KR7ksAX0tOFotCrvYXjkCsr3x7kLD2+GMVJhDTpS6CdrW6J74xdaHo KH768kK+PDYHBwGFjtSCQDK1+6IkaowxJNavZy0JJ2jQLUJCCutTZRuDFypq6cRa6MRLAq remUama9eA3fuheTERoMI3qe1bcJdsuwCWUjJU+m5fZIv3C5Cpp7qrkl4OvrTg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1673861332; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=G5OPga9s9el+CHbJ947Z6+l1jBqfCaiyuLxg70TImQI=; b=VQufeeKpZGn1kYgRPd4AKwfCq0hIRDSc47/Oz8WNSfT25i+HGUAF2uC/Fg26A9SBHNpLPv o/ph6TS07ugK64CA== From: "tip-bot2 for Yair Podemsky" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] x86/aperfmperf: Erase stale arch_freq_scale values when disabling frequency invariance readings Cc: Yair Podemsky , Ingo Molnar , Peter Zijlstra , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230110160206.75912-1-ypodemsk@redhat.com> References: <20230110160206.75912-1-ypodemsk@redhat.com> MIME-Version: 1.0 Message-ID: <167386133169.4906.2168836143666979819.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 5f5cc9ed992cbab6361f198966f0edba5fc52688 Gitweb: https://git.kernel.org/tip/5f5cc9ed992cbab6361f198966f0edba5fc52688 Author: Yair Podemsky AuthorDate: Tue, 10 Jan 2023 18:02:06 +02:00 Committer: Ingo Molnar CommitterDate: Mon, 16 Jan 2023 10:19:15 +01:00 x86/aperfmperf: Erase stale arch_freq_scale values when disabling frequency invariance readings Once disable_freq_invariance_work is called the scale_freq_tick function will not compute or update the arch_freq_scale values. However the scheduler will still read these values and use them. The result is that the scheduler might perform unfair decisions based on stale values. This patch adds the step of setting the arch_freq_scale values for all cpus to the default (max) value SCHED_CAPACITY_SCALE, Once all cpus have the same arch_freq_scale value the scaling is meaningless. Signed-off-by: Yair Podemsky Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20230110160206.75912-1-ypodemsk@redhat.com --- arch/x86/kernel/cpu/aperfmperf.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c index 1f60a2b..fdbb5f0 100644 --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -330,7 +330,16 @@ static void __init bp_init_freq_invariance(void) static void disable_freq_invariance_workfn(struct work_struct *work) { + int cpu; + static_branch_disable(&arch_scale_freq_key); + + /* + * Set arch_freq_scale to a default value on all cpus + * This negates the effect of scaling + */ + for_each_possible_cpu(cpu) + per_cpu(arch_freq_scale, cpu) = SCHED_CAPACITY_SCALE; } static DECLARE_WORK(disable_freq_invariance_work,