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 3D022C4332F for ; Wed, 9 Nov 2022 15:49:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229937AbiKIPty (ORCPT ); Wed, 9 Nov 2022 10:49:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229787AbiKIPtv (ORCPT ); Wed, 9 Nov 2022 10:49:51 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C7B513F7C for ; Wed, 9 Nov 2022 07:49:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=KTmaf8B87vIIN0yxDModoNqGQTj0xX5ooslpdKUP19Q=; b=OIr0butA3iITJ8k+7dXjKRZ8hc tp6wfV3Ll9bJiI0H1jR0pyZBtXtc5qhOUsowRUyIV19G+CE0Uk3xffbL2pyrHnexeLOt8IlIptkby NzA9qr28coz2FadXnD/6HRXTu6r1j/U8qPh9F5iR4TTCmU0x4Dgl64j0oTzONTAmKl7X+JfZ+9hXS nYyYGFGt4c14vfSxto40NdGp1D2ZquV9cSG4DmXqlRr/4a1752UMxn37PR6AzsqFNYMiUnZovFH3B 9TGuAinAb6YLC2dFNjwbblQ22bByUg/WWb6PAziBwQGO9QtXQ83qI+aunzODEiQGqe/1+L9++97lj W0HVtUJA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1osnKW-00BIwI-NF; Wed, 09 Nov 2022 15:49:32 +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)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D803B30031B; Wed, 9 Nov 2022 16:49:25 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AB11820D9067D; Wed, 9 Nov 2022 16:49:25 +0100 (CET) Date: Wed, 9 Nov 2022 16:49:25 +0100 From: Peter Zijlstra To: Qais Yousef Cc: Kajetan Puchalski , Jian-Min Liu , Dietmar Eggemann , Ingo Molnar , Vincent Guittot , Morten Rasmussen , Vincent Donnefort , Quentin Perret , Patrick Bellasi , Abhijeet Dharmapurikar , Qais Yousef , linux-kernel@vger.kernel.org, Jonathan JMChen Subject: Re: [RFC PATCH 0/1] sched/pelt: Change PELT halflife at runtime Message-ID: References: <20220829055450.1703092-1-dietmar.eggemann@arm.com> <0f82011994be68502fd9833e499749866539c3df.camel@mediatek.com> <20221108194843.i4qckcu7zwqstyis@airbuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221108194843.i4qckcu7zwqstyis@airbuntu> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 08, 2022 at 07:48:43PM +0000, Qais Yousef wrote: > On 11/07/22 14:41, Peter Zijlstra wrote: > > On Thu, Sep 29, 2022 at 03:41:47PM +0100, Kajetan Puchalski wrote: > > > > > Based on all the tests we've seen, jankbench or otherwise, the > > > improvement can mainly be attributed to the faster ramp up of frequency > > > caused by the shorter PELT window while using schedutil. > > > > Would something terrible like the below help some? > > > > If not, I suppose it could be modified to take the current state as > > history. But basically it runs a faster pelt sum along side the regular > > signal just for ramping up the frequency. > > A bit of a tangent, but this reminded me of this old patch: > > https://lore.kernel.org/lkml/1623855954-6970-1-git-send-email-yt.chang@mediatek.com/ > > I think we have a bit too many moving cogs that might be creating undesired > compound effect. > > Should we consider removing margins in favour of improving util ramp up/down? > (whether via util_est or pelt hf). Yeah, possibly. So one thing that was key to that hack I proposed is that it is per-task. This means we can either set or detect the task activation period and use that to select an appropriate PELT multiplier. But please explain; once tasks are in a steady state (60HZ, 90HZ or god forbit higher), the utilization should be the same between the various PELT window sizes, provided the activation period isn't *much* larger than the window. Are these things running a ton of single shot tasks or something daft like that?