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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF78CECAAD2 for ; Mon, 29 Aug 2022 14:35:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230099AbiH2OfO (ORCPT ); Mon, 29 Aug 2022 10:35:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229748AbiH2OfM (ORCPT ); Mon, 29 Aug 2022 10:35:12 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 152E5C46 for ; Mon, 29 Aug 2022 07:35:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=C6mBiXZi1ynVUoBONfK85Dgqx8UibnwjC8ne4PTssys=; b=qJqUH9BWmC2sLjfD6Sqnxx+6Ev ed2iqQt2qiCA+Psi9O63a1TVNQbcOrzPuLiFaNHUWtktIsPs4AkvzdFxg0sJIMJuUrqF1aqwfzI6f 5AdMNBGpZhDsY3UQdDkuPt9jCAksaBR7iFMr8VYXZ3qbrkRpNAKSp89hiCiYlUfH0iHH/Zv89BwL/ K7tV8KUfRWG/x4QXen3PnYtS9qwm05xsGkVPdxdtAYN3pezj6Q4LPhfXN1d9qhrj4kk0t2wkxMmLb jo771iHIKKy50EBOUjNLfqu2b+wiGAKXNIoyI9r/skwXUj4sfvcjXzkk4nlOzIHBAeq7h3dDDAzGx /MLaniHQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oSfqg-007WKQ-Fb; Mon, 29 Aug 2022 14:34:47 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 3BB0F300410; Mon, 29 Aug 2022 16:34:39 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 203462097DAD0; Mon, 29 Aug 2022 16:34:39 +0200 (CEST) Date: Mon, 29 Aug 2022 16:34:39 +0200 From: Peter Zijlstra To: Quentin Perret Cc: Vincent Guittot , Dietmar Eggemann , Ingo Molnar , Morten Rasmussen , Vincent Donnefort , Patrick Bellasi , Abhijeet Dharmapurikar , Jian-Min , Qais Yousef , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 1/1] sched/pelt: Introduce PELT multiplier Message-ID: References: <20220829055450.1703092-1-dietmar.eggemann@arm.com> <20220829055450.1703092-2-dietmar.eggemann@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 29, 2022 at 02:23:17PM +0000, Quentin Perret wrote: > I'll let folks in CC comment about their use-case in more details, but > there's definitely been an interest in tuning this thing at run-time An interest and it making sense are two very distinct things that bear no relation to one another in any way. > FWIW. Typically a larger half-life will be fine with predictable > workloads with little inputs from users (e.g. fullscreen video playback) > while a lower one can be preferred in highly interactive cases (games, As per always; consider the combined workload. > ...). The transient state is fun to reason about, but it really > shouldn't be too common AFAIK. Once you give away control there is no taking it back, and userspace *will* do stupid things and expect unicorns. > With that said I'd quite like to see numbers to back that claim. > Measuring power while running a video (for instance) with various HL > values should help. And similarly it shouldn't be too hard to get > performance numbers. I'm thinking this all needs far more than mere numbers to justify.