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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 4C81FC433E9 for ; Mon, 15 Mar 2021 09:51:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06FC364EB2 for ; Mon, 15 Mar 2021 09:51:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229599AbhCOJvZ (ORCPT ); Mon, 15 Mar 2021 05:51:25 -0400 Received: from foss.arm.com ([217.140.110.172]:56520 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbhCOJvS (ORCPT ); Mon, 15 Mar 2021 05:51:18 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 347921FB; Mon, 15 Mar 2021 02:51:18 -0700 (PDT) Received: from [10.57.12.51] (unknown [10.57.12.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 213063F70D; Mon, 15 Mar 2021 02:51:15 -0700 (PDT) Subject: Re: [PATCH] thermal: power_allocator: using round the division when re-divvying up power To: gao.yunxiao6@gmail.com, daniel.lezcano@linaro.org Cc: rui.zhang@intel.com, amitk@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, orsonzhai@gmail.com, zhang.lyra@gmail.com, "jeson.gao" References: <1615796737-4688-1-git-send-email-gao.yunxiao6@gmail.com> From: Lukasz Luba Message-ID: <9c14451e-be6f-0713-4c26-8b67e1fa51a5@arm.com> Date: Mon, 15 Mar 2021 09:51:14 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <1615796737-4688-1-git-send-email-gao.yunxiao6@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/15/21 8:25 AM, gao.yunxiao6@gmail.com wrote: > From: "jeson.gao" > > The division is used directly in re-divvying up power, the decimal part will > be discarded, devices will get less than the extra_actor_power - 1. > if using round the division to make the calculation more accurate. > > For example: > actor0 received more than it's max_power, it has the extra_power 759 > actor1 received less than it's max_power, it require extra_actor_power 395 > actor2 received less than it's max_power, it require extra_actor_power 365 > actor1 and actor2 require the total capped_extra_power 760 > > using division in re-divvying up power > actor1 would actually get the extra_actor_power 394 > actor2 would actually get the extra_actor_power 364 > > if using round the division in re-divvying up power > actor1 would actually get the extra_actor_power 394 > actor2 would actually get the extra_actor_power 365 > > Signed-off-by: Jeson Gao > --- > drivers/thermal/gov_power_allocator.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c > index 92acae53df49..2802a0e13c88 100644 > --- a/drivers/thermal/gov_power_allocator.c > +++ b/drivers/thermal/gov_power_allocator.c > @@ -374,9 +374,11 @@ static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors, > */ > extra_power = min(extra_power, capped_extra_power); > if (capped_extra_power > 0) > - for (i = 0; i < num_actors; i++) > - granted_power[i] += (extra_actor_power[i] * > - extra_power) / capped_extra_power; > + for (i = 0; i < num_actors; i++) { > + u64 extra_range = (u64)extra_actor_power[i] * extra_power; > + granted_power[i] += DIV_ROUND_CLOSEST_ULL(extra_range, > + capped_extra_power); > + } > } > > static int allocate_power(struct thermal_zone_device *tz, > Make sense. There is already DIV_ROUND_CLOSEST_ULL() in that function, so let's align both. There might be a bit overhead on 32bit machines, but IPA polling isn't so often there. Reviewed-by: Lukasz Luba Regards, Lukasz