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,URIBL_BLOCKED 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 314FEC433EF for ; Tue, 19 Jun 2018 10:49:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E30702083D for ; Tue, 19 Jun 2018 10:49:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E30702083D 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 S937613AbeFSKt3 (ORCPT ); Tue, 19 Jun 2018 06:49:29 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47436 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937551AbeFSKt1 (ORCPT ); Tue, 19 Jun 2018 06:49:27 -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 79E591435; Tue, 19 Jun 2018 03:49:27 -0700 (PDT) Received: from e108498-lin.cambridge.arm.com (e108498-lin.cambridge.arm.com [10.1.211.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 860B73F25D; Tue, 19 Jun 2018 03:49:23 -0700 (PDT) Date: Tue, 19 Jun 2018 11:49:22 +0100 From: Quentin Perret To: Juri Lelli Cc: Pavan Kondeti , peterz@infradead.org, rjw@rjwysocki.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joelaf@google.com, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [RFC PATCH v3 10/10] arch_topology: Start Energy Aware Scheduling Message-ID: <20180619104921.GV17720@e108498-lin.cambridge.arm.com> References: <20180521142505.6522-1-quentin.perret@arm.com> <20180521142505.6522-11-quentin.perret@arm.com> <20180619091841.GD9208@codeaurora.org> <20180619094002.GR17720@e108498-lin.cambridge.arm.com> <20180619094714.GA13617@localhost.localdomain> <20180619100224.GT17720@e108498-lin.cambridge.arm.com> <20180619101901.GC13617@localhost.localdomain> <20180619102502.GU17720@e108498-lin.cambridge.arm.com> <20180619103108.GD13617@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180619103108.GD13617@localhost.localdomain> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 19 Jun 2018 at 12:31:08 (+0200), Juri Lelli wrote: > On 19/06/18 11:25, Quentin Perret wrote: > > On Tuesday 19 Jun 2018 at 12:19:01 (+0200), Juri Lelli wrote: > > > On 19/06/18 11:02, Quentin Perret wrote: > > > > On Tuesday 19 Jun 2018 at 11:47:14 (+0200), Juri Lelli wrote: > > > > > On 19/06/18 10:40, Quentin Perret wrote: > > > > > > Hi Pavan, > > > > > > > > > > > > On Tuesday 19 Jun 2018 at 14:48:41 (+0530), Pavan Kondeti wrote: > > > > > > > > > > [...] > > > > > > > > > > > > There seems to be a sysfs interface exposed by this driver to change cpu_scale. > > > > > > > Should we worry about it? I don't know what is the usecase for changing the > > > > > > > cpu_scale from user space. > > > > > > > > > > > > This is something I've been wondering as well. TBH, I'm not sure what to > > > > > > do in this case. And I'm not sure to know what is the use-case either. > > > > > > Debugging purpose I assume ? > > > > > > > > > > > > Juri, did you have a specific use-case for this feature when the > > > > > > arch_topology driver was first introduced ? Or was it just to align > > > > > > with the existing arm/arm64 code ? > > > > > > > > > > It was requested (IIRC) because DT might have bogus values and not be > > > > > easily modifiable. So, this is another way to get things right for your > > > > > platform at runtime. > > > > > > > > Right, but that also allows you to set different capacities to CPUs > > > > inside the same freq domain, which isn't supported by the EM framework, > > > > at least for now. So I would prefer to assume that your values in DT must > > > > to be correct to use EAS, and leave the code as-is for now. > > > > > > It's actually built on the (current) assumption that siblings share > > > capacity [1], so it seems to align with what EM requires. > > > > > > [1] https://elixir.bootlin.com/linux/latest/source/drivers/base/arch_topology.c#L71 > > > > But there is not hard guarantee that the core_sibling mask and the > > frequency domains are aligned :-( > > > > Hikey 620 is an example where they might be misaligned (I think) > > Yep. In this case you'd need to write cpu_capacity twice (for each > cluster). I think. Ok, I'll keep the code as-is for now, and we can discuss further on v4. I guess we need to agree on the need for em_rescale_cpu_capacity() before going too deep in the Arm-specific changes to call it :-) Thanks ! Quentin