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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT 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 32692C43381 for ; Wed, 13 Mar 2019 16:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0947320693 for ; Wed, 13 Mar 2019 16:12:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726513AbfCMQMf (ORCPT ); Wed, 13 Mar 2019 12:12:35 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60018 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725888AbfCMQMf (ORCPT ); Wed, 13 Mar 2019 12:12:35 -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 C150080D; Wed, 13 Mar 2019 09:12:34 -0700 (PDT) Received: from e110439-lin (e110439-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CD2E13F71D; Wed, 13 Mar 2019 09:12:31 -0700 (PDT) Date: Wed, 13 Mar 2019 16:12:29 +0000 From: Patrick Bellasi To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting Message-ID: <20190313161229.pkib2tmjass5chtb@e110439-lin> References: <20190208100554.32196-1-patrick.bellasi@arm.com> <20190208100554.32196-2-patrick.bellasi@arm.com> <20190313134022.GB5922@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190313134022.GB5922@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13-Mar 14:40, Peter Zijlstra wrote: > On Fri, Feb 08, 2019 at 10:05:40AM +0000, Patrick Bellasi wrote: > > +static inline unsigned int uclamp_bucket_id(unsigned int clamp_value) > > +{ > > + return clamp_value / UCLAMP_BUCKET_DELTA; > > +} > > + > > +static inline unsigned int uclamp_bucket_value(unsigned int clamp_value) > > +{ > > + return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value); > > return clamp_value - (clamp_value % UCLAMP_BUCKET_DELTA); > > might generate better code; just a single division, instead of a div and > mult. Wondering if compilers cannot do these optimizations... but yes, looks cool and will do it in v8, thanks. > > +} > > + > > +static inline unsigned int uclamp_none(int clamp_id) > > +{ > > + if (clamp_id == UCLAMP_MIN) > > + return 0; > > + return SCHED_CAPACITY_SCALE; > > +} > > + > > +static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id) > > +{ > > + struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket; > > + unsigned int max_value = uclamp_none(clamp_id); > > + unsigned int bucket_id; > > + > > + /* > > + * Both min and max clamps are MAX aggregated, thus the topmost > > + * bucket with some tasks defines the rq's clamp value. > > + */ > > + bucket_id = UCLAMP_BUCKETS; > > + do { > > + --bucket_id; > > + if (!rq->uclamp[clamp_id].bucket[bucket_id].tasks) > > + continue; > > + max_value = bucket[bucket_id].value; > > + break; > > If you flip the if condition the code will be nicer. > > > + } while (bucket_id); > > But you can also use a for loop: > > for (i = UCLAMP_BUCKETS-1; i>=0; i--) { > if (rq->uclamp[clamp_id].bucket[i].tasks) { > max_value = bucket[i].value; > break; > } > } Yes, the for looks better, but perhaps like that: unsigned int bucket_id = UCLAMP_BUCKETS; /* * Both min and max clamps are MAX aggregated, thus the topmost * bucket with some tasks defines the rq's clamp value. */ for (; bucket_id >= 0; --bucket_id) { if (!bucket[bucket_id].tasks) continue; max_value = bucket[bucket_id].value; break; } ... just to save a {} block. > > + WRITE_ONCE(rq->uclamp[clamp_id].value, max_value); > > +} -- #include Patrick Bellasi