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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,USER_IN_DEF_DKIM_WL 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 6D271ECDFB8 for ; Tue, 24 Jul 2018 17:11:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 285FC20844 for ; Tue, 24 Jul 2018 17:11:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LlTDDUEE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 285FC20844 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.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 S2388610AbeGXSTX (ORCPT ); Tue, 24 Jul 2018 14:19:23 -0400 Received: from mail-io0-f193.google.com ([209.85.223.193]:34632 "EHLO mail-io0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388467AbeGXSTX (ORCPT ); Tue, 24 Jul 2018 14:19:23 -0400 Received: by mail-io0-f193.google.com with SMTP id l7-v6so4041883ioj.1 for ; Tue, 24 Jul 2018 10:11:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=GU92F4OTBoMC2haJ9enew6pJIwqBhp/7Wiyd72zRXgw=; b=LlTDDUEEbMA9HW0jZwHzh5wab8SI/TJjihGHWEVoL0HsdM84w/L7yEz0q2FCWHmLk3 HE+vhMbZ5VjHcfGuaDN/w9s1gC3BeVW3AB95S8Y6bexdHAogoHfusjGyj4xTK89YOmYJ DkWJXeyVsvzJX8Q5zDv31ir0flkkClvubq3Q0lgKNEGtOcEoZtWKNFzTB0jHTJshJ0yZ f0BrriTHgwwr502lLLQ51JD8AiopigeoMR325D5GrgmB0/ZSlaupfkLK/HtjOjCK+K2d +MQgOvpB2EjoJ2pONY0ew4LCsJ6LBf6aJkbELWmHf/6PxuZKPfZgsKcPWWG/7fpQDdgH /k5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=GU92F4OTBoMC2haJ9enew6pJIwqBhp/7Wiyd72zRXgw=; b=UIeLlvxGj8sIAgoKQIIXOMESrbKH7vRJRuwAhy3FWnvqMlhIQAUYma8cU5OLVL4v7P hdl3jxRIJqRYU7coDzD+ST1oMFkYGiGsV2dSq8JP2IGKQYsgkZjaTiemsHqWm/W/hMJg HIdJZuZc+cu+ykrC/cHRvsBHV0mi3Fq5Bip3U27Uj3AG48Pd0MMI690hm7TQYgK9scBp ZS/tl7xkEWOf6FC0/ZN7KNmkZrz9yNSVJ+0i04AV+r1U9XaVGsjTCM8mWAnnT2DXdOWU 7FxM4s5DX0IEgJ3cTg5OMLoc7t3MRFRq2H4WfLc35cG85g21lWO1w1Fe+UzgOVFuz4gW c+SQ== X-Gm-Message-State: AOUpUlEJx3NoRh/Q5W80QJh8sEbmSEhJBk01Li9tBRDGkPuttBKgpebJ w6uleYsY4PrAJKyFTBB1s5W/fZRQbL25lWXY4Rdu5g== X-Google-Smtp-Source: AAOMgpcTg2AyWS38CjV2wVLpGTnlIKrzzKfvbrfWVVzMmkbt4xD3ols1DtWl0a0KWwzsx6XC8Ib29EO2+ORzxDKnHSE= X-Received: by 2002:a5e:8341:: with SMTP id y1-v6mr2181207iom.183.1532452315260; Tue, 24 Jul 2018 10:11:55 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:ac0:e445:0:0:0:0:0 with HTTP; Tue, 24 Jul 2018 10:11:54 -0700 (PDT) In-Reply-To: <20180724164303.GB3162@e110439-lin> References: <20180716082906.6061-1-patrick.bellasi@arm.com> <20180716082906.6061-13-patrick.bellasi@arm.com> <20180724164303.GB3162@e110439-lin> From: Suren Baghdasaryan Date: Tue, 24 Jul 2018 10:11:54 -0700 Message-ID: Subject: Re: [PATCH v2 12/12] sched/core: uclamp: use percentage clamp values To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 24, 2018 at 9:43 AM, Patrick Bellasi wrote: > On 21-Jul 21:04, Suren Baghdasaryan wrote: >> On Mon, Jul 16, 2018 at 1:29 AM, Patrick Bellasi >> wrote: > > [...] > >> > +static inline unsigned int scale_from_percent(unsigned int pct) >> > +{ >> > + WARN_ON(pct > 100); >> > + >> > + return ((SCHED_FIXEDPOINT_SCALE * pct) / 100); >> > +} >> > + >> > +static inline unsigned int scale_to_percent(unsigned int value) >> > +{ >> > + unsigned int rounding = 0; >> > + >> > + WARN_ON(value > SCHED_FIXEDPOINT_SCALE); >> > + >> > + /* Compensate rounding errors for: 0, 256, 512, 768, 1024 */ >> > + if (likely((value & 0xFF) && ~(value & 0x700))) >> > + rounding = 1; >> >> Hmm. I don't think ~(value & 0x700) will ever yield FALSE... What am I missing? > > So, 0x700 is the topmost 3 bits sets (111 0000 0000) which different > configuration corresponds to: > > 001 0000 0000 => 256 > 010 0000 0000 => 512 > 011 0000 0000 => 768 > 100 0000 0000 => 1024 > > Thus, if 0x700 matches then we have one of these values in input and > for these cases we have to add a unit to the percentage value. > > For the case (value == 0) we translate it into 0% thanks to the check > on (value & 0xFF) to ensure rounding = 0. > I think just (value & 0xFF) is enough to get you the right behavior. ~(value & 0x700) is not needed, it's effectively a NoOp which always yields TRUE. For any *value* (value & 0x700) == 0x...00 and ~(value & 0x700) == 0x...FF == TRUE. > Here is a small python snippet I've used to check the conversion of > all the possible percentage values: > > ---8<--- > values = range(0, 101) > for pct in xrange(0, 101): > util = int((1024 * pct) / 100) > rounding = 1 > if not ((util & 0xFF) and ~(util & 0x700)): > print "Fixing util_to_perc({:3d} => {:4d})".format(pct, util) > rounding = 0 > pct2 = (rounding + ((100 * util) / 1024)) > if pct2 in values: > values.remove(pct2) > if pct != pct2: > print "Convertion failed for: {:3d} => {:4d} => {:3d}".format(pct, util, pct2) > if values: > print "ERROR: not all percentage values converted" > ---8<--- > > -- > #include > > Patrick Bellasi