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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 5D8D8C4363A for ; Wed, 21 Oct 2020 19:47:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F20C124171 for ; Wed, 21 Oct 2020 19:47:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438783AbgJUTrz (ORCPT ); Wed, 21 Oct 2020 15:47:55 -0400 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:38802 "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409957AbgJUTry (ORCPT ); Wed, 21 Oct 2020 15:47:54 -0400 X-IronPort-AV: E=Sophos;i="5.77,402,1596492000"; d="scan'208";a="362429807" Received: from abo-173-121-68.mrs.modulonet.fr (HELO hadrien) ([85.68.121.173]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2020 21:47:51 +0200 Date: Wed, 21 Oct 2020 21:47:51 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: "Rafael J. Wysocki" cc: Julia Lawall , Peter Zijlstra , Mel Gorman , Ingo Molnar , kernel-janitors@vger.kernel.org, Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , linux-kernel@vger.kernel.org, Valentin Schneider , Gilles Muller , viresh.kumar@linaro.org, srinivas.pandruvada@linux.intel.com Subject: Re: [PATCH] sched/fair: check for idle core In-Reply-To: <20581608.8Dxr8OdOFj@kreacher> Message-ID: References: <1603211879-1064-1-git-send-email-Julia.Lawall@inria.fr> <20201021121950.GF2628@hirez.programming.kicks-ass.net> <20581608.8Dxr8OdOFj@kreacher> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Oct 2020, Rafael J. Wysocki wrote: > On Wednesday, October 21, 2020 2:42:20 PM CEST Julia Lawall wrote: > > > > On Wed, 21 Oct 2020, Peter Zijlstra wrote: > > > > > On Wed, Oct 21, 2020 at 01:56:55PM +0200, Julia Lawall wrote: > > > > Prior to 5.8, my machine was using intel_pstate and had few background > > > > tasks. Thus the problem wasn't visible in practice. Starting with 5.8 > > > > the kernel decided that intel_cpufreq would be more appropriate, which > > > > introduced kworkers every 0.004 seconds on all cores. > > > > > > That still doesn't make any sense. Are you running the legacy on-demand > > > thing or something? > > > > > > Rafael, Srinivas, Viresh, how come it defaults to that? > > > > The relevant commits are 33aa46f252c7, and 39a188b88332 that fixes a small > > bug. I have a Intel(R) Xeon(R) CPU E7-8870 v4 @ 2.10GHz that does not > > have the HWP feature, even though the cores seemed to be able to change > > their frequencies at the hardware level. > > That's in the range of "turbo" P-states (if a P-state above a certain threshold > is requested by the governor, the processor has a license to choose P-states > in the range above this threshold by itself). Sorry, but I don't understand this answer at all. thanks, julia