From patchwork Fri Mar 9 09:39:27 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: 10270263 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 288A560211 for ; Fri, 9 Mar 2018 09:50:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 191B829DA5 for ; Fri, 9 Mar 2018 09:50:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0CBD729DBB; Fri, 9 Mar 2018 09:50:28 +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=-6.9 required=2.0 tests=BAYES_00,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 8EA5029DA5 for ; Fri, 9 Mar 2018 09:50:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750937AbeCIJu0 (ORCPT ); Fri, 9 Mar 2018 04:50:26 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:54017 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbeCIJsv (ORCPT ); Fri, 9 Mar 2018 04:48:51 -0500 Received: from 79.184.254.228.ipv4.supernova.orange.pl (79.184.254.228) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83) id 1cd6ad25bdcef088; Fri, 9 Mar 2018 10:48:49 +0100 From: "Rafael J. Wysocki" To: Peter Zijlstra , Linux PM , Frederic Weisbecker Cc: Thomas Gleixner , Paul McKenney , Thomas Ilsche , Doug Smythies , Rik van Riel , Aubrey Li , Mike Galbraith , LKML Subject: [RFC/RFT][PATCH v3 3/6] sched: idle: Do not stop the tick before cpuidle_idle_call() Date: Fri, 09 Mar 2018 10:39:27 +0100 Message-ID: <1731836.ePJh9sqWU9@aspire.rjw.lan> In-Reply-To: <2450532.XN8DODrtDf@aspire.rjw.lan> References: <2450532.XN8DODrtDf@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 Make cpuidle_idle_call() decide whether or not to stop the tick. First, the cpuidle_enter_s2idle() path deals with the tick (and with the entire timekeeping for that matter) by itself and it doesn't need the tick to be stopped beforehand. Second, to address the issue with short idle duration predictions by the idle governor after the tick has been stopped, it will be necessary to change the ordering of cpuidle_select() with respect to tick_nohz_idle_stop_tick(). To prepare for that, put a tick_nohz_idle_stop_tick() call in the same branch in which cpuidle_select() is called. Signed-off-by: Rafael J. Wysocki --- kernel/sched/idle.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) Index: linux-pm/kernel/sched/idle.c =================================================================== --- linux-pm.orig/kernel/sched/idle.c +++ linux-pm/kernel/sched/idle.c @@ -146,13 +146,15 @@ static void cpuidle_idle_call(void) } /* - * Tell the RCU framework we are entering an idle section, - * so no more rcu read side critical sections and one more + * The RCU framework needs to be told that we are entering an idle + * section, so no more rcu read side critical sections and one more * step to the grace period */ - rcu_idle_enter(); if (cpuidle_not_available(drv, dev)) { + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + default_idle_call(); goto exit_idle; } @@ -169,16 +171,26 @@ static void cpuidle_idle_call(void) if (idle_should_enter_s2idle() || dev->use_deepest_state) { if (idle_should_enter_s2idle()) { + rcu_idle_enter(); + entered_state = cpuidle_enter_s2idle(drv, dev); if (entered_state > 0) { local_irq_enable(); goto exit_idle; } + + rcu_idle_exit(); } + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + next_state = cpuidle_find_deepest_state(drv, dev); call_cpuidle(drv, dev, next_state); } else { + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + /* * Ask the cpuidle framework to choose a convenient idle state. */ @@ -241,12 +253,11 @@ static void do_idle(void) * broadcast device expired for us, we don't want to go deep * idle as we know that the IPI is going to arrive right away. */ - if (cpu_idle_force_poll || tick_check_broadcast_expired()) { + if (cpu_idle_force_poll || tick_check_broadcast_expired()) cpu_idle_poll(); - } else { - tick_nohz_idle_stop_tick(); + else cpuidle_idle_call(); - } + arch_cpu_idle_exit(); }