From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADC93C4332D for ; Thu, 11 Mar 2021 12:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C2BC64FDF for ; Thu, 11 Mar 2021 12:38:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233330AbhCKMhh (ORCPT ); Thu, 11 Mar 2021 07:37:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:59780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233167AbhCKMhX (ORCPT ); Thu, 11 Mar 2021 07:37:23 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A41F864FE7; Thu, 11 Mar 2021 12:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615466243; bh=tWJG8XyIOuDvmB3DrOnKsLIOoV6EuxGTr/dpTqOJcm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OQiTBJxmJ8J8whPrtGyYb2wD1fdS3xLxSaCWC//ZxAK8Bckgu/ex8e/KjkJDFjL4F S+/ICE5SJHo80mCVN4BXiI2uFkbS/qGu77aFccXe3lPB97/7lJZX7/skT5VZO7FAbV +QdvNVBYd2WMg0CAUoqvw7eUfiIhqMcAyxLft9khHffFYbqFDSrJNFzhOe8QDOtADa TtWncVc6SZcVVzP0cZKlABchPJaggb7yF7Qpz+7t4MHEf5/CLzCUPTTuP5otRv52ze lJJ70X4ttubgRXpHFknmRJOFSEYo4LSIIENotBQe/aADhFr+ahQVqBD0ys1zcFF8pE XrEUqocDEmqvg== From: Frederic Weisbecker To: Peter Zijlstra , Thomas Gleixner Cc: LKML , Yunfeng Ye , "Rafael J . Wysocki" , Ti Zhou , Frederic Weisbecker , "Paul E . McKenney" , Marcelo Tosatti , Ingo Molnar Subject: [PATCH 03/10] tick/nohz: Conditionally restart tick on idle exit Date: Thu, 11 Mar 2021 13:37:01 +0100 Message-Id: <20210311123708.23501-4-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210311123708.23501-1-frederic@kernel.org> References: <20210311123708.23501-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yunfeng Ye In nohz_full mode, switching from idle to a task will unconditionally issue a tick restart. If the task is alone in the runqueue or is the highest priority, the tick will fire once then eventually stop. But that alone is still undesired noise. Therefore, only restart the tick on idle exit when it's strictly necessary. Signed-off-by: Yunfeng Ye Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Marcelo Tosatti Cc: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- kernel/time/tick-sched.c | 50 ++++++++++++++++++++++++---------------- 1 file changed, 30 insertions(+), 20 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index af76cfa51b57..77dc8cd61dc8 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -922,26 +922,30 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) tick_nohz_restart(ts, now); } -static void tick_nohz_full_update_tick(struct tick_sched *ts) +static void __tick_nohz_full_update_tick(struct tick_sched *ts, + ktime_t now) { #ifdef CONFIG_NO_HZ_FULL - int cpu; - - if (!tick_nohz_full_this_cpu()) - return; - - if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) - return; - - cpu = smp_processor_id(); + int cpu = smp_processor_id(); if (can_stop_full_tick(cpu, ts)) tick_nohz_stop_sched_tick(ts, cpu); else if (ts->tick_stopped) - tick_nohz_restart_sched_tick(ts, ktime_get()); + tick_nohz_restart_sched_tick(ts, now); #endif } +static void tick_nohz_full_update_tick(struct tick_sched *ts) +{ + if (!tick_nohz_full_this_cpu()) + return; + + if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) + return; + + __tick_nohz_full_update_tick(ts, ktime_get()); +} + static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) { /* @@ -1209,18 +1213,24 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts) #endif } -static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now) -{ - tick_nohz_restart_sched_tick(ts, now); - tick_nohz_account_idle_ticks(ts); -} - void tick_nohz_idle_restart_tick(void) { struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); - if (ts->tick_stopped) - __tick_nohz_idle_restart_tick(ts, ktime_get()); + if (ts->tick_stopped) { + tick_nohz_restart_sched_tick(ts, ktime_get()); + tick_nohz_account_idle_ticks(ts); + } +} + +static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now) +{ + if (tick_nohz_full_this_cpu()) + __tick_nohz_full_update_tick(ts, now); + else + tick_nohz_restart_sched_tick(ts, now); + + tick_nohz_account_idle_ticks(ts); } /** @@ -1252,7 +1262,7 @@ void tick_nohz_idle_exit(void) tick_nohz_stop_idle(ts, now); if (tick_stopped) - __tick_nohz_idle_restart_tick(ts, now); + tick_nohz_idle_update_tick(ts, now); local_irq_enable(); } -- 2.25.1