Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752071AbaG1RlA (ORCPT ); Mon, 28 Jul 2014 13:41:00 -0400 Received: from mail-we0-f179.google.com ([74.125.82.179]:58981 "EHLO mail-we0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751162AbaG1Rhs (ORCPT ); Mon, 28 Jul 2014 13:37:48 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Ingo Molnar , Nicolas Pitre , "Paul E. McKenney" , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Viresh Kumar Subject: [PATCH 02/10] nohz: Kick full dynticks timer targets with an empty IPI Date: Mon, 28 Jul 2014 19:37:28 +0200 Message-Id: <1406569056-30217-3-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1406569056-30217-1-git-send-email-fweisbec@gmail.com> References: <1406569056-30217-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While we enqueue a new timer on a dynticks target, we must send it an IPI so that it reschedules the next tick accordingly. Now all we need for that is to run irq_exit() on the target. Hence an empty IRQ is way enough. We don't need to run tick_nohz_full_check() and all the overhead that comes with the several cmpxchg() necessary for irq work list and state progress. So lets use a void irq work instead. Cc: Ingo Molnar Cc: Nicolas Pitre Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Viresh Kumar Signed-off-by: Frederic Weisbecker --- kernel/sched/core.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7f3063c..171f9ce 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -685,15 +685,13 @@ static void wake_up_idle_cpu(int cpu) static bool wake_up_full_nohz_cpu(int cpu) { /* - * We just need the target to call irq_exit() and re-evaluate - * the next tick. The nohz full kick at least implies that. - * If needed we can still optimize that later with an - * empty IRQ. + * Kick the target to make it call irq_exit() and re-evaluate + * the next tick. */ if (tick_nohz_full_cpu(cpu)) { if (cpu != smp_processor_id() || tick_nohz_tick_stopped()) - tick_nohz_full_kick_cpu(cpu); + kick_cpu_async(cpu); return true; } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/