From patchwork Mon Oct 15 11:53:25 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 10641625 X-Patchwork-Delegate: rjw@sisk.pl Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C6DD318FD for ; Mon, 15 Oct 2018 11:57:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B3F5428FFC for ; Mon, 15 Oct 2018 11:57:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A80222952E; Mon, 15 Oct 2018 11:57:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 447E128FFC for ; Mon, 15 Oct 2018 11:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726557AbeJOTmU (ORCPT ); Mon, 15 Oct 2018 15:42:20 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:47634 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726319AbeJOTmU (ORCPT ); Mon, 15 Oct 2018 15:42:20 -0400 Received: from 79.184.253.168.ipv4.supernova.orange.pl (79.184.253.168) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.148) id d46cfa9caa594898; Mon, 15 Oct 2018 13:57:21 +0200 From: "Rafael J. Wysocki" To: Linux PM Cc: LKML , Peter Zijlstra , Daniel Lezcano , Doug Smythies Subject: [PATCH 2/2] cpuidle: menu: Avoid computations when result will be discarded Date: Mon, 15 Oct 2018 13:53:25 +0200 Message-ID: <3958974.INltPUcQCY@aspire.rjw.lan> In-Reply-To: <9077862.OKK49htnqA@aspire.rjw.lan> References: <9077862.OKK49htnqA@aspire.rjw.lan> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rafael J. Wysocki If the minimum interval taken into account in the average computation loop in get_typical_interval() is less than the expected idle duration determined so far, the resultant average cannot be greater than that value as well and the entire return result of the function is going to be discarded anyway going forward. In that case, it is a waste of time to carry out the remaining computations in get_typical_interval(), so avoid that by returning early if the minimum interval is not below the expected idle duration. No intentional changes of behavior. Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/menu.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) Index: linux-pm/drivers/cpuidle/governors/menu.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/menu.c +++ linux-pm/drivers/cpuidle/governors/menu.c @@ -196,10 +196,11 @@ static void menu_update(struct cpuidle_d * of points is below a threshold. If it is... then use the * average of these 8 points as the estimated value. */ -static unsigned int get_typical_interval(struct menu_device *data) +static unsigned int get_typical_interval(struct menu_device *data, + unsigned int predicted_us) { int i, divisor; - unsigned int max, thresh, avg; + unsigned int min, max, thresh, avg; uint64_t sum, variance; thresh = UINT_MAX; /* Discard outliers above this value */ @@ -207,6 +208,7 @@ static unsigned int get_typical_interval again: /* First calculate the average of past intervals */ + min = UINT_MAX; max = 0; sum = 0; divisor = 0; @@ -217,8 +219,19 @@ again: divisor++; if (value > max) max = value; + + if (value < min) + min = value; } } + + /* + * If the result of the computation is going to be discarded anyway, + * avoid the computation altogether. + */ + if (min >= predicted_us) + return UINT_MAX; + if (divisor == INTERVALS) avg = sum >> INTERVAL_SHIFT; else @@ -325,7 +338,7 @@ static int menu_select(struct cpuidle_dr /* * Use the lowest expected idle interval to pick the idle state. */ - predicted_us = min(predicted_us, get_typical_interval(data)); + predicted_us = min(predicted_us, get_typical_interval(data, predicted_us)); if (tick_nohz_tick_stopped()) { /*