From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AA7FE24A041; Mon, 30 Jun 2025 10:07:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751278031; cv=none; b=WKkKAPd8tQqBmVarO699OttEW5Om7JIvqFp766GLOKMfultChK74eEYrCg83127xj4DXvr+Mekw/kIrDIwnPzuc37gD1/qf+jD7QmmMgvYZVhKxvtBpBA31oUoRDaF5q9viCz1ryLLTxmdE+zhlgJv3SHNKNsMAX72GlWDZFVDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751278031; c=relaxed/simple; bh=BBC7Jiocg90QkWAgP3ev2DTS4q8/YMW6mfcj5aBowm4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aoN6Q4laJkENMK+Z4X1SFWKs9/LXoMe317PG/rTbNYTdAa3GkAy+NaabkkNAgElksxklStr8H3viMbwxm0nPuPMyCQhUDhcAVUInSRiqO/5f5DA594kQw5QUKLSmBoPDVcihhIYVbr790oYmmL1QGGHc4s5NuUjQxCiqTdTFi4g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 3521E1D34; Mon, 30 Jun 2025 03:06:53 -0700 (PDT) Received: from [10.57.85.50] (unknown [10.57.85.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DADD13F58B; Mon, 30 Jun 2025 03:07:06 -0700 (PDT) Message-ID: <5afe2400-659d-40d8-ab4f-33a1b250ac85@arm.com> Date: Mon, 30 Jun 2025 11:07:12 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 00/10] PM: EM: Add netlink support for the energy model. To: Changwoo Min Cc: christian.loehle@arm.com, tj@kernel.org, pavel@kernel.org, len.brown@intel.com, rafael@kernel.org, kernel-dev@igalia.com, linux-pm@vger.kernel.org, sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" References: <20250613094428.267791-1-changwoo@igalia.com> Content-Language: en-US From: Lukasz Luba In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Changwoo, On 6/27/25 04:37, Changwoo Min wrote: > Gentle ping as it reaches 2-weeks. My apologies for delay on that topic. Let me have a look into this... > > @Lukasz, @Rafael -- I have a question related to the energy model > in general. As far as I understand, the energy model describes > the performance-energy consumption tradeoff when a single CPU in > a performance domain is running. However, in reality, SoCs may > have thermal constraints, which would result in additional > constraints. For example, running all CPUs with the highest > frequency may not be possible. My question is this: does kernel > maintain and use such (thermal?) constraints? That's true in real scenarios on mobile SoCs, running with max freq on all CPUs is possible likely only for short period... The Energy Model itself doesn't handle such situation. The code in thermal framework and in Energy Aware Scheduler has feature to handle it and know which top OPPs are not possible to be used. Although, the EM in such situation is likely to be adjusted, because the SoC temperature reaches high values. Especially if that heat was generated by the GPU not CPUs themselves, then it's extra leakage will be accounted and EM data modified in runtime. Another scenario when the EM might be updated is when Middleware will recognize a known 'scenario' e.g. long video conference with camera in use (thus Image Signal Processor, which also can heat the SoC, like GPU). Or a 'preferred profile' for light-weight application using some HW decoding, e.g. video playback and thus some CPUs are more preferred by EAS to be used in it (EM might change the energy efficiency gently for such CPUs). Regards, Lukasz