From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934257AbeCHPOR (ORCPT ); Thu, 8 Mar 2018 10:14:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:38668 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933478AbeCHPON (ORCPT ); Thu, 8 Mar 2018 10:14:13 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE6D12133D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=frederic@kernel.org Date: Thu, 8 Mar 2018 16:14:10 +0100 From: Frederic Weisbecker To: "Rafael J. Wysocki" Cc: Peter Zijlstra , Linux PM , Thomas Gleixner , Frederic Weisbecker , Paul McKenney , Thomas Ilsche , Doug Smythies , Rik van Riel , Aubrey Li , Mike Galbraith , LKML Subject: Re: [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code Message-ID: <20180308151407.GA11118@lerouge> References: <2067762.1uWBf5RSRc@aspire.rjw.lan> <4136227.b9g9WnMbNJ@aspire.rjw.lan> <20180307231827.GA9367@lerouge> <1938066.lrFpnYERYl@aspire.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1938066.lrFpnYERYl@aspire.rjw.lan> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 08, 2018 at 10:22:26AM +0100, Rafael J. Wysocki wrote: > On Thursday, March 8, 2018 12:18:29 AM CET Frederic Weisbecker wrote: > > On Tue, Mar 06, 2018 at 10:02:01AM +0100, Rafael J. Wysocki wrote: > > > Index: linux-pm/kernel/time/tick-sched.c > > > =================================================================== > > > --- linux-pm.orig/kernel/time/tick-sched.c > > > +++ linux-pm/kernel/time/tick-sched.c > > > + > > > +/** > > > + * tick_nohz_idle_prepare - prepare for entering idle on the current CPU. > > > + * > > > + * Called when we start the idle loop. > > > + */ > > > +void tick_nohz_idle_prepare(void) > > > +{ > > > + struct tick_sched *ts; > > > + > > > + __tick_nohz_idle_prepare(); > > > + > > > + local_irq_disable(); > > > + > > > + ts = this_cpu_ptr(&tick_cpu_sched); > > > + ts->inidle = 1; > > > + > > > + local_irq_enable(); > > > +} > > > > Why not calling tick_nohz_start_idle() from there? This is going to > > simplify the rest, you won't need to call tick_nohz_idle_go_idle() > > from places that don't want to stop the tick and you can then remove > > the stop_tick argument. > > So I guess I would then use ts->idle_entrytime as "now" in the > tick_nohz_get_sleep_length() computation, right? Ah right, I missed the need for ktime_get(). You can't use ts->idle_entrytime in tick_nohz_get_sleep_length() because full dynticks doesn't rely on it. But I think you can just do the following, with a comment explaining that idle_entrytime is expected to be fresh enough at this point: diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 57b3de4..8e61796 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -923,7 +923,7 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts, bool stop_tick) ts->idle_calls++; - expires = tick_nohz_stop_sched_tick(ts, now, cpu); + expires = tick_nohz_stop_sched_tick(ts, ts->idle_entrytime, cpu); if (expires > 0LL) { ts->idle_sleeps++; ts->idle_expires = expires;