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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 411BBC07E9B for ; Mon, 19 Jul 2021 10:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2846E61006 for ; Mon, 19 Jul 2021 10:31:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236304AbhGSJuw (ORCPT ); Mon, 19 Jul 2021 05:50:52 -0400 Received: from foss.arm.com ([217.140.110.172]:55012 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236110AbhGSJuo (ORCPT ); Mon, 19 Jul 2021 05:50:44 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AA7E1ED1; Mon, 19 Jul 2021 03:31:24 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C46F63F73D; Mon, 19 Jul 2021 03:31:23 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Vincent Guittot , Peter Zijlstra , Ingo Molnar , Dietmar Eggemann Subject: [PATCH v2 1/2] sched/fair: Add NOHZ balancer flag for nohz.next_balance updates Date: Mon, 19 Jul 2021 11:31:16 +0100 Message-Id: <20210719103117.3624936-2-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210719103117.3624936-1-valentin.schneider@arm.com> References: <20210719103117.3624936-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A following patch will trigger NOHZ idle balances as a means to update nohz.next_balance. Vincent noted that blocked load updates can have non-negligible overhead, which should be avoided if the intent is to only update nohz.next_balance. Add a new NOHZ balance kick flag, NOHZ_NEXT_KICK. Gate NOHZ blocked load update by the presence of NOHZ_STATS_KICK - currently all NOHZ balance kicks will have the NOHZ_STATS_KICK flag set, so no change in behaviour is expected. Suggested-by: Vincent Guittot Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 9 ++++++--- kernel/sched/sched.h | 8 +++++++- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 11d22943753f..5c88698c3664 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10506,7 +10506,8 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, * setting the flag, we are sure to not clear the state and not * check the load of an idle cpu. */ - WRITE_ONCE(nohz.has_blocked, 0); + if (flags & NOHZ_STATS_KICK) + WRITE_ONCE(nohz.has_blocked, 0); /* * Ensures that if we miss the CPU, we must see the has_blocked @@ -10528,13 +10529,15 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, * balancing owner will pick it up. */ if (need_resched()) { - has_blocked_load = true; + if (flags & NOHZ_STATS_KICK) + has_blocked_load = true; goto abort; } rq = cpu_rq(balance_cpu); - has_blocked_load |= update_nohz_stats(rq); + if (flags & NOHZ_STATS_KICK) + has_blocked_load |= update_nohz_stats(rq); /* * If time for next balance is due, diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9a1c6aeb9165..b0f38b5d2550 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2695,12 +2695,18 @@ extern void cfs_bandwidth_usage_dec(void); #define NOHZ_BALANCE_KICK_BIT 0 #define NOHZ_STATS_KICK_BIT 1 #define NOHZ_NEWILB_KICK_BIT 2 +#define NOHZ_NEXT_KICK_BIT 3 +/* Run rebalance_domains() */ #define NOHZ_BALANCE_KICK BIT(NOHZ_BALANCE_KICK_BIT) +/* Update blocked load */ #define NOHZ_STATS_KICK BIT(NOHZ_STATS_KICK_BIT) +/* Update blocked load when entering idle */ #define NOHZ_NEWILB_KICK BIT(NOHZ_NEWILB_KICK_BIT) +/* Update nohz.next_balance */ +#define NOHZ_NEXT_KICK BIT(NOHZ_NEXT_KICK_BIT) -#define NOHZ_KICK_MASK (NOHZ_BALANCE_KICK | NOHZ_STATS_KICK) +#define NOHZ_KICK_MASK (NOHZ_BALANCE_KICK | NOHZ_STATS_KICK | NOHZ_NEXT_KICK) #define nohz_flags(cpu) (&cpu_rq(cpu)->nohz_flags) -- 2.25.1