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=-0.6 required=5.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID 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 B7B61C43143 for ; Thu, 13 Sep 2018 19:14:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 737D921477 for ; Thu, 13 Sep 2018 19:14:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QZdn44VC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 737D921477 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1728391AbeINAZU (ORCPT ); Thu, 13 Sep 2018 20:25:20 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33780 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727560AbeINAZU (ORCPT ); Thu, 13 Sep 2018 20:25:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=kQqF44iSaC/2GXba2pvHI10oNcBtoe3SJvjDaOOgK90=; b=QZdn44VCcxW2zM4/uR3H/e7s/ UuGp54RzQhKn3rBGXm7W9RwroxudXwRXICDsc9xZqdANwV4KfRKJlIgEows7f8+mxLGqLIKtsBcMs pSCUAZ9MP5nwNLUryT+4vzh85sNNX6fC8oVBm3onKxOxEJoAvq+DifDyU8T4ZL9OnnbxDT8Kid1c/ 0S5xH2ud1wwOP1xEtdIUGad5+UqyTNqVCLfqyrmtapqRqxJKD+nA6591T8IxHvuPADEyIWRbftOm8 aGYox8hrATQn+O3AH+3MxA/f8uRtuD0CE7LjopFulqUOYgjFW4XO5jJsx5Ifbr/1NYS8tf3FmmWGl Oke7piFFw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1g0X4K-0005FY-0N; Thu, 13 Sep 2018 19:14:24 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A89D2202C1A34; Thu, 13 Sep 2018 21:14:22 +0200 (CEST) Date: Thu, 13 Sep 2018 21:14:22 +0200 From: Peter Zijlstra To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v4 02/16] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Message-ID: <20180913191422.GZ24082@hirez.programming.kicks-ass.net> References: <20180828135324.21976-1-patrick.bellasi@arm.com> <20180828135324.21976-3-patrick.bellasi@arm.com> <20180912134945.GZ24106@hirez.programming.kicks-ass.net> <20180912155619.GG1413@e110439-lin> <20180912161218.GW24082@hirez.programming.kicks-ass.net> <20180912173515.GH1413@e110439-lin> <20180912174236.GB24106@hirez.programming.kicks-ass.net> <20180912175202.GK1413@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180912175202.GK1413@e110439-lin> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 12, 2018 at 06:52:02PM +0100, Patrick Bellasi wrote: > On 12-Sep 19:42, Peter Zijlstra wrote: > > On Wed, Sep 12, 2018 at 06:35:15PM +0100, Patrick Bellasi wrote: > > > On 12-Sep 18:12, Peter Zijlstra wrote: > > > > > > No idea; but if you want to go all fancy you can replace he whole > > > > uclamp_map thing with something like: > > > > > > > > struct uclamp_map { > > > > union { > > > > struct { > > > > unsigned long v : 10; > > > > unsigned long c : BITS_PER_LONG - 10; > > > > }; > > > > atomic_long_t s; > > > > }; > > > > }; > > > > > > That sounds really cool and scary at the same time :) > > > > > > The v:10 requires that we never set SCHED_CAPACITY_SCALE>1024 > > > or that we use it to track a percentage value (i.e. [0..100]). > > > > Or we pick 11 bits, it seems unlikely that capacity be larger than 2k. > > Just remembered a past experience where we had unaligned access traps > on some machine because... don't you see any potentially issue on > using bitfleds like you suggest above ? > > I'm thinking to: > > commit 317d359df95d ("sched/core: Force proper alignment of 'struct util_est'") There should not be (and I'm still confused by that particular commit you reference). If we access everything through the uclamp_map::s, and only use the bitfields to interpret the results, it all 'works'. The tricky thing we did earlier was trying to use u64 accesses for 2 u32 variables. And somehow ia64 didn't get the alignment right.