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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 B3CA4ECE58D for ; Wed, 9 Oct 2019 14:26:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BC9C20B7C for ; Wed, 9 Oct 2019 14:26:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729865AbfJIO0Q (ORCPT ); Wed, 9 Oct 2019 10:26:16 -0400 Received: from foss.arm.com ([217.140.110.172]:35562 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727769AbfJIO0Q (ORCPT ); Wed, 9 Oct 2019 10:26:16 -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 19D451576; Wed, 9 Oct 2019 07:26:15 -0700 (PDT) Received: from [192.168.0.9] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CB8103F71A; Wed, 9 Oct 2019 07:26:12 -0700 (PDT) Subject: Re: [RFC v5 4/6] sched/fair: Tune task wake-up logic to pack small background tasks on fewer cores To: Parth Shah , Vincent Guittot Cc: linux-kernel , "open list:THERMAL" , Peter Zijlstra , Ingo Molnar , Patrick Bellasi , Valentin Schneider , Pavel Machek , Doug Smythies , Quentin Perret , "Rafael J. Wysocki" , Tim Chen , Daniel Lezcano References: <20191007083051.4820-1-parth@linux.ibm.com> <20191007083051.4820-5-parth@linux.ibm.com> <80bb34ec-6358-f4dc-d20d-cde6c9d7e197@linux.ibm.com> <86dc25e4-9f19-627f-9581-d74608b7f20c@linux.ibm.com> From: Dietmar Eggemann Message-ID: Date: Wed, 9 Oct 2019 16:26:03 +0200 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: <86dc25e4-9f19-627f-9581-d74608b7f20c@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 09/10/2019 10:57, Parth Shah wrote: [...] >> On 07/10/2019 18:53, Parth Shah wrote: >>> >>> >>> On 10/7/19 5:49 PM, Vincent Guittot wrote: >>>> On Mon, 7 Oct 2019 at 10:31, Parth Shah wrote: [...] >>> Maybe I can add just below the sched_energy_present(){...} construct giving >>> precedence to EAS? I'm asking this because I remember Patrick telling me to >>> leverage task packing for android as well? >> >> I have a hard time imaging that Turbosched will be used in Android next >> to EAS in the foreseeable future. >> >> First of all, EAS provides task packing already on Performance Domain >> (PD) level (a.k.a. as cluster on traditional 2-cluster Arm/Arm64 >> big.LITTLE or DynamIQ (with Phantom domains (out of tree solution)). >> This is where we can safe energy without harming latency. >> >> See the tests results under '2.1 Energy test case' in >> >> https://lore.kernel.org/r/20181203095628.11858-1-quentin.perret@arm.com >> >> There are 10 to 50 small (classified solely by task utilization) tasks >> per test case and EAS shows an effect on energy consumption by packing >> them onto the PD (cluster) of the small CPUs. >> >> And second, the CPU supported topology is different to the one you're >> testing on. >> > > cool. I was just keeping in mind the following quote > " defining a generic spread-vs-pack wakeup policy which is something > Android also could benefit from " (https://lkml.org/lkml/2019/6/28/628) The main thing is that in case we want to introduce a new functionality into CFS, we should try hard to use existing infrastructure (or infrastructure there is agreement on that we'll need it) as much as possible. If I understand Patrick here correctly, he suggested not to use uclamp but the task latency nice approach. There is agreement that we would need something like this as infrastructure: https://lore.kernel.org/r/20190830174944.21741-1-subhra.mazumdar@oracle.com So p->latency_nice is suitable to include your p->flags |= PF_CAN_BE_PACKED concept nicely. > > BTW, IIUC that does task consolidation only on single CPU unless > rd->overload is set, right? Task consolidation on Performance Domains (PDs) w/ multiple CPUs (e.g. on a per-cluster PD big.LITTLE system) only works when the system is not overutilized: 6326 int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) 6327 { ... 6337 if (!pd || *READ_ONCE(rd->overutilized)*) 6338 goto fail; ... [...]