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=-2.3 required=3.0 tests=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 F2942ECE587 for ; Tue, 1 Oct 2019 14:15:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D185E20842 for ; Tue, 1 Oct 2019 14:15:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388693AbfJAOPb (ORCPT ); Tue, 1 Oct 2019 10:15:31 -0400 Received: from foss.arm.com ([217.140.110.172]:50592 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726554AbfJAOPa (ORCPT ); Tue, 1 Oct 2019 10:15:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 305A11000; Tue, 1 Oct 2019 07:15:30 -0700 (PDT) Received: from [10.1.194.37] (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 292883F71A; Tue, 1 Oct 2019 07:15:29 -0700 (PDT) Subject: Re: [PATCH v2 0/4] sched/fair: Active balancer RT/DL preemption fix To: Juri Lelli Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, tglx@linutronix.de, qais.yousef@arm.com, Steven Rostedt References: <20190815145107.5318-1-valentin.schneider@arm.com> <20191001133115.GC6481@localhost.localdomain> From: Valentin Schneider Message-ID: Date: Tue, 1 Oct 2019 15:15:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191001133115.GC6481@localhost.localdomain> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Juri, On 01/10/2019 14:31, Juri Lelli wrote: > Hi Valentin, > > On 01/10/19 11:29, Valentin Schneider wrote: >> (expanded the Cc list) >> RT/DL folks, any thought on the thing? > > Even if I like your idea and it looks theoretically the right thing to > do, I'm not sure we want it in practice if it adds complexity to CFS. > > I personally never noticed this kind of interference from CFS, but, at > the same time, for RT we usually like more to be safe than sorry. > However, since this doesn't seem to be bullet-proof (as you also say), I > guess it all boils down again to complexity vs. practical benefits. > Thanks for having a look. IMO worst part is the local detach_one_task() thing, I added that after v1 following Qais' comments but perhaps it doesn't gain us much. I'll try to cook something up with rt-app and see if I can get sensible numbers. > Best, > > Juri >