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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F12FDC433F5 for ; Tue, 9 Nov 2021 13:53:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0BE8610A2 for ; Tue, 9 Nov 2021 13:53:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234089AbhKIN4Y (ORCPT ); Tue, 9 Nov 2021 08:56:24 -0500 Received: from foss.arm.com ([217.140.110.172]:34088 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231137AbhKIN4Y (ORCPT ); Tue, 9 Nov 2021 08:56:24 -0500 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 26AAF2B; Tue, 9 Nov 2021 05:53:38 -0800 (PST) Received: from [10.57.26.224] (unknown [10.57.26.224]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D33FB3F70D; Tue, 9 Nov 2021 05:53:34 -0800 (PST) Subject: Re: [PATCH 6/7] thermal: netlink: Add a new event to notify CPU capabilities change To: Srinivas Pandruvada Cc: Ricardo Neri , "Rafael J. Wysocki" , Daniel Lezcano , linux-pm@vger.kernel.org, x86@kernel.org, linux-doc@vger.kernel.org, Len Brown , Aubrey Li , Amit Kucheria , Andi Kleen , Tim Chen , "Ravi V. Shankar" , Ricardo Neri , linux-kernel@vger.kernel.org References: <20211106013312.26698-1-ricardo.neri-calderon@linux.intel.com> <20211106013312.26698-7-ricardo.neri-calderon@linux.intel.com> <2160a0b8-59ec-03a1-1fd5-a3f98085be07@arm.com> From: Lukasz Luba Message-ID: <5e4d7661-1e91-0c72-ae02-b2c60c2ad95e@arm.com> Date: Tue, 9 Nov 2021 13:53:32 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Srinivas, On 11/9/21 1:23 PM, Srinivas Pandruvada wrote: > Hi Lukasz, > > On Tue, 2021-11-09 at 12:39 +0000, Lukasz Luba wrote: >> Hi Ricardo, >> >> >> On 11/6/21 1:33 AM, Ricardo Neri wrote: >>> From: Srinivas Pandruvada >>> >>> Add a new netlink event to notify change in CPU capabilities in >>> terms of >>> performance and efficiency. >> >> Is this going to be handled by some 'generic' tools? If yes, maybe >> the values for 'performance' might be aligned with capacity >> [0,1024] ? Or are they completely not related so the mapping is >> simply impossible? >> > > That would have been very useful. > > The problem is that we may not know the maximum performance as system > may be booting with few CPUs (using maxcpus kernel command line) and > then user hot adding them. So we may need to rescale when we get a new > maximum performance CPU and send to user space. > > We can't just use max from HFI table at in instance as it is not > necessary that HFI table contains data for all CPUs. > > If HFI max performance value of 255 is a scaled value to max > performance CPU value in the system, then this conversion would have > been easy. But that is not. I see. I was asking because I'm working on similar interface and just wanted to understand your approach better. In my case we would probably simply use 'capacity' scale, or more precisely available capacity after subtracting 'thermal pressure' value. That might confuse a generic tool which listens to these socket messages, though. So probably I would have to add a new THERMAL_GENL_ATTR_CPU_CAPABILITY_* id to handle this different normalized across CPUs scale.