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 1D995C388F9 for ; Wed, 21 Oct 2020 12:42:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7DF422249 for ; Wed, 21 Oct 2020 12:42:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440749AbgJUMmt (ORCPT ); Wed, 21 Oct 2020 08:42:49 -0400 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:46320 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390624AbgJUMmt (ORCPT ); Wed, 21 Oct 2020 08:42:49 -0400 X-IronPort-AV: E=Sophos;i="5.77,401,1596492000"; d="scan'208";a="473679023" Received: from 173.121.68.85.rev.sfr.net (HELO hadrien) ([85.68.121.173]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2020 14:42:21 +0200 Date: Wed, 21 Oct 2020 14:42:20 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: Peter Zijlstra cc: Julia Lawall , 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 , "Rafael J. Wysocki" , viresh.kumar@linaro.org, srinivas.pandruvada@linux.intel.com Subject: Re: [PATCH] sched/fair: check for idle core In-Reply-To: <20201021121950.GF2628@hirez.programming.kicks-ass.net> Message-ID: References: <1603211879-1064-1-git-send-email-Julia.Lawall@inria.fr> <20201021112038.GC32041@suse.de> <20201021121950.GF2628@hirez.programming.kicks-ass.net> 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, 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. julia From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Date: Wed, 21 Oct 2020 12:42:20 +0000 Subject: Re: [PATCH] sched/fair: check for idle core Message-Id: List-Id: References: <1603211879-1064-1-git-send-email-Julia.Lawall@inria.fr> <20201021112038.GC32041@suse.de> <20201021121950.GF2628@hirez.programming.kicks-ass.net> In-Reply-To: <20201021121950.GF2628@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Zijlstra Cc: Julia Lawall , 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 , "Rafael J. Wysocki" , viresh.kumar@linaro.org, srinivas.pandruvada@linux.intel.com 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. julia