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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 C6426ECDFB1 for ; Tue, 17 Jul 2018 08:15:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 810AD20C09 for ; Tue, 17 Jul 2018 08:15:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Ccdf6mPO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 810AD20C09 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729997AbeGQIqg (ORCPT ); Tue, 17 Jul 2018 04:46:36 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:42012 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726396AbeGQIqg (ORCPT ); Tue, 17 Jul 2018 04:46:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=J+gstwVCFqlFfgmxoxh72LkjINTd93YeXG+7psn/6k0=; b=Ccdf6mPOrV211mcPKW8Jld0CC AYIqIq7I1TaQUWgW3trJjkrz+xo6EX5w3oTIs3OwAvhDSXf5jaEknIP7kER2Qvy/AaEoDTwAezJRL DdkfKaugZmv8V2O6aL6npbGvJIvN9NYjAdEYtojD5uz1EaFgBMak9mYwFgHiiyJ0yw4adCO5MH2gv imEtdq9czUwZsb++gDPgXLHxugBXwiHTleINvTwQTDNcEZ1lzk5+Ud0cWrMwm84v2JruLbShT4OuY +lsh9zIZshM3pyLz/IX9CS0AHJ33uo6x7fq5M4Updlz3oNeF+GZ7Fonn02Tz0n1DSoOEhSgJL4i1O Iu+sUAfTg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ffL8Y-0002tl-CV; Tue, 17 Jul 2018 08:15:10 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E9F8A20275F36; Tue, 17 Jul 2018 10:15:07 +0200 (CEST) Date: Tue, 17 Jul 2018 10:15:07 +0200 From: Peter Zijlstra To: Andreas Herrmann Cc: "Rafael J. Wysocki" , Frederic Weisbecker , Viresh Kumar , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq Message-ID: <20180717081507.GS2476@hirez.programming.kicks-ass.net> References: <20180717065048.74mmgk4t5utjaa6a@suselix> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717065048.74mmgk4t5utjaa6a@suselix> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 17, 2018 at 08:50:48AM +0200, Andreas Herrmann wrote: > I've recently noticed that commit 554c8aa8ecad ("sched: idle: Select > idle state before stopping the tick") causes severe performance drop > for systems using pcc-cpufreq driver. Depending on the number of CPUs > the system might be almost unusable. Have you looked at that driver? It features a global lock which is taken for all cpufreq operations. Once you get past a handful of cpus that will constrict your system exactly as you say. What kind of machine are you running this on, and can you configure the thing to use anything else? If so, do so and never look back.