From patchwork Thu Jul 25 09:03:02 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: preeti X-Patchwork-Id: 2833273 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 5ECA59F243 for ; Thu, 25 Jul 2013 09:08:09 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 47FB120216 for ; Thu, 25 Jul 2013 09:08:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 264ED2010C for ; Thu, 25 Jul 2013 09:08:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755249Ab3GYJIG (ORCPT ); Thu, 25 Jul 2013 05:08:06 -0400 Received: from e28smtp03.in.ibm.com ([122.248.162.3]:42194 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752418Ab3GYJFh (ORCPT ); Thu, 25 Jul 2013 05:05:37 -0400 Received: from /spool/local by e28smtp03.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Thu, 25 Jul 2013 14:28:37 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 8D0093940053; Thu, 25 Jul 2013 14:35:23 +0530 (IST) Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r6P96Mgu32964678; Thu, 25 Jul 2013 14:36:22 +0530 Received: from d28av01.in.ibm.com (loopback [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r6P95KOJ021248; Thu, 25 Jul 2013 09:05:27 GMT Received: from preeti.in.ibm.com (preeti.in.ibm.com [9.124.35.49]) by d28av01.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r6P95JaH021148; Thu, 25 Jul 2013 09:05:19 GMT Subject: [RFC PATCH 4/5] cpuidle/ppc: CPU goes tickless if there are no arch-specific constraints To: benh@kernel.crashing.org, paul.gortmaker@windriver.com, paulus@samba.org, shangw@linux.vnet.ibm.com, galak@kernel.crashing.org, fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, michael@ellerman.id.au, arnd@arndb.de, linux-pm@vger.kernel.org, rostedt@goodmis.org, rjw@sisk.pl, john.stultz@linaro.org, tglx@linutronix.de, chenhui.zhao@freescale.com, deepthi@linux.vnet.ibm.com, geoff@infradead.org, linux-kernel@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, schwidefsky@de.ibm.com, svaidy@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org From: Preeti U Murthy Date: Thu, 25 Jul 2013 14:33:02 +0530 Message-ID: <20130725090302.12500.42998.stgit@preeti.in.ibm.com> In-Reply-To: <20130725090016.12500.28888.stgit@preeti.in.ibm.com> References: <20130725090016.12500.28888.stgit@preeti.in.ibm.com> User-Agent: StGit/0.16-38-g167d MIME-Version: 1.0 X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13072508-3864-0000-0000-000009402A1D Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In the current design of timer offload framework, the broadcast cpu should *not* go into tickless idle so as to avoid missed wakeups on CPUs in deep idle states. Since we prevent the CPUs entering deep idle states from programming the lapic of the broadcast cpu for their respective next local events for reasons mentioned in PATCH[3/5], the broadcast CPU checks if there are any CPUs to be woken up during each of its timer interrupt programmed to its local events. With tickless idle, the broadcast CPU might not get a timer interrupt till after many ticks which can result in missed wakeups on CPUs in deep idle states. By disabling tickless idle, worst case, the tick_sched hrtimer will trigger a timer interrupt every period to check for broadcast. However the current setup of tickless idle does not let us make the choice of tickless on individual cpus. NOHZ_MODE_INACTIVE which disables tickless idle, is a system wide setting. Hence resort to an arch specific call to check if a cpu can go into tickless idle. Signed-off-by: Preeti U Murthy --- arch/powerpc/kernel/time.c | 5 +++++ kernel/time/tick-sched.c | 7 +++++++ 2 files changed, 12 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 8ed0fb3..68a636f 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -862,6 +862,11 @@ static void decrementer_timer_broadcast(const struct cpumask *mask) arch_send_tick_broadcast(mask); } +int arch_can_stop_idle_tick(int cpu) +{ + return cpu != bc_cpu; +} + static void register_decrementer_clockevent(int cpu) { struct clock_event_device *dec = &per_cpu(decrementers, cpu); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 6960172..e9ffa84 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -700,8 +700,15 @@ static void tick_nohz_full_stop_tick(struct tick_sched *ts) #endif } +int __weak arch_can_stop_idle_tick(int cpu) +{ + return 1; +} + static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) { + if (!arch_can_stop_idle_tick(cpu)) + return false; /* * If this cpu is offline and it is the one which updates * jiffies, then give up the assignment and let it be taken by