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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 8D6BEC6778A for ; Tue, 24 Jul 2018 08:59:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45B2220874 for ; Tue, 24 Jul 2018 08:59:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 45B2220874 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 S2388301AbeGXKEu (ORCPT ); Tue, 24 Jul 2018 06:04:50 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:45602 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388136AbeGXKEu (ORCPT ); Tue, 24 Jul 2018 06:04:50 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 25D117A9; Tue, 24 Jul 2018 01:59:24 -0700 (PDT) Received: from [10.4.12.120] (e107158-lin.Emea.Arm.com [10.4.12.120]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BA1B43F237; Tue, 24 Jul 2018 01:59:22 -0700 (PDT) Subject: Re: [PATCH 1/4] sched/topology: SD_ASYM_CPUCAPACITY flag detection To: Morten Rasmussen Cc: vincent.guittot@linaro.org, peterz@infradead.org, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, mingo@redhat.com, valentin.schneider@arm.com, linux-arm-kernel@lists.infradead.org References: <1532093554-30504-1-git-send-email-morten.rasmussen@arm.com> <1532093554-30504-2-git-send-email-morten.rasmussen@arm.com> <20180723152551.GA29978@e105550-lin.cambridge.arm.com> <20180724083710.GB29978@e105550-lin.cambridge.arm.com> From: Qais Yousef Message-ID: <0d9598fa-28c1-0851-4d40-2cc97a5317b5@arm.com> Date: Tue, 24 Jul 2018 09:59:21 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180724083710.GB29978@e105550-lin.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/07/18 09:37, Morten Rasmussen wrote: > On Mon, Jul 23, 2018 at 05:07:50PM +0100, Qais Yousef wrote: >> On 23/07/18 16:27, Morten Rasmussen wrote: >>> It does increase the cost of things like hotplug slightly and >>> repartitioning of root_domains a slightly but I don't see how we can >>> avoid it if we want generic code to set this flag. If the costs are not >>> acceptable I think the only option is to make the detection architecture >>> specific. >> I think hotplug is already expensive and this overhead would be small in >> comparison. But this could be called when frequency changes if I understood >> correctly - this is the one I wasn't sure how 'hot' it could be. I wouldn't >> expect frequency changes at a very high rate because it's relatively >> expensive too.. > A frequency change shouldn't lead to a flag change or a rebuild of the > sched_domain hierarhcy. The situations where the hierarchy should be > rebuild to update the flag is during boot as we only know the amount of > asymmetry once cpufreq has been initialized, when cpus are hotplugged > in/out, and when root_domains change due to cpuset reconfiguration. So > it should be a relatively rare event. Ah OK I misunderstood that part then. The series LGTM then. -- Qais Yousef