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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 B90FBC6778D for ; Wed, 12 Sep 2018 17:52:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CE7E2087F for ; Wed, 12 Sep 2018 17:52:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CE7E2087F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 S1727809AbeILW5p (ORCPT ); Wed, 12 Sep 2018 18:57:45 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:36794 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727231AbeILW5p (ORCPT ); Wed, 12 Sep 2018 18:57:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3C01E7A9; Wed, 12 Sep 2018 10:52:08 -0700 (PDT) Received: from e110439-lin (e110439-lin.Emea.Arm.com [10.4.12.126]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6CF273F557; Wed, 12 Sep 2018 10:52:05 -0700 (PDT) Date: Wed, 12 Sep 2018 18:52:02 +0100 From: Patrick Bellasi To: Peter Zijlstra 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: <20180912175202.GK1413@e110439-lin> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180912174236.GB24106@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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'") -- #include Patrick Bellasi