From patchwork Thu Jan 28 17:12:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 373789 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=-19.3 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 9A1E4C433E6 for ; Thu, 28 Jan 2021 17:20:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D42064E14 for ; Thu, 28 Jan 2021 17:20:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232932AbhA1RUR (ORCPT ); Thu, 28 Jan 2021 12:20:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:51650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232812AbhA1RSI (ORCPT ); Thu, 28 Jan 2021 12:18:08 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8D17A64E25; Thu, 28 Jan 2021 17:13:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611853985; bh=ODAPEU8mEkBB577u6jw8N9nhc90ro0nsWiFFejTP+10=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=edcS/ieiloWpWb2wOXM8fzMvZxrDoeqiV0BFb41qeKSxFWhHrLSR7BmVuzcICKnON GOE49ugdcWX2G0x15yzrOjjHAK/eq6hYCLu0xlnhva9gh7XuJJy5AWYxxmdwf9rSUT znIA7laVeOmHjPu5N4D5Ek2udngOaJl7oOfeQrVLIeAPm4ksWCLkZHf04LM/UQITtm RPXlf0pmQh89LGMxKsOuvvJD2WYbB/WDbdEzBzLVEVIfbemKBw0VFtKtsuDEwsXZEJ G84sqPeJjUBtsLCGdTEOq804DkQj6e11AFuL/Q9TBR2qq2qYy4z7D+aNK1rblm2wPc 3ZaA/woMEOldw== From: Frederic Weisbecker To: "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , Boqun Feng , Lai Jiangshan , Neeraj Upadhyay , Josh Triplett , Stable , Joel Fernandes Subject: [PATCH 15/16] rcu/nocb: Prepare for finegrained deferred wakeup Date: Thu, 28 Jan 2021 18:12:21 +0100 Message-Id: <20210128171222.131380-16-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210128171222.131380-1-frederic@kernel.org> References: <20210128171222.131380-1-frederic@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Provide a way to tune the deferred wakeup level we want to perform from a safe wakeup point. Currently those sites are: * nocb_timer * user/idle/guest entry * CPU down * softirq/rcuc All of these sites perform the wake up for both RCU_NOCB_WAKE and RCU_NOCB_WAKE_FORCE. In order to merge nocb_timer and nocb_bypass_timer together, we plan to add a new RCU_NOCB_WAKE_BYPASS that really want to be deferred until a timer fires so that we don't wake up the NOCB-gp kthread too early. To prepare for that, integrate a wake up level/limit that a callsite is deemed to perform. Signed-off-by: Frederic Weisbecker Cc: Josh Triplett Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Neeraj Upadhyay Cc: Boqun Feng --- kernel/rcu/tree.c | 2 +- kernel/rcu/tree.h | 2 +- kernel/rcu/tree_plugin.h | 15 ++++++++------- 3 files changed, 10 insertions(+), 9 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f74a9ba62c12..e31b1d8fde93 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3813,7 +3813,7 @@ static int rcu_pending(int user) check_cpu_stall(rdp); /* Does this CPU need a deferred NOCB wakeup? */ - if (rcu_nocb_need_deferred_wakeup(rdp)) + if (rcu_nocb_need_deferred_wakeup(rdp, RCU_NOCB_WAKE)) return 1; /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index b280a843bd2c..2510e86265c1 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -433,7 +433,7 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, bool *was_alldone, unsigned long flags); static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, unsigned long flags); -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); static void rcu_spawn_cpu_nocb_kthread(int cpu); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index b1f76f341c66..162dda3714f1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2354,13 +2354,14 @@ static int rcu_nocb_cb_kthread(void *arg) } /* Is a deferred wakeup of rcu_nocb_kthread() required? */ -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level) { - return READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT; + return READ_ONCE(rdp->nocb_defer_wakeup) >= level; } /* Do a deferred wakeup of rcu_nocb_kthread(). */ -static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp) +static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp, + int level) { unsigned long flags; int ndw; @@ -2369,7 +2370,7 @@ static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp) raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); - if (!rcu_nocb_need_deferred_wakeup(rdp_gp)) { + if (!rcu_nocb_need_deferred_wakeup(rdp_gp, level)) { raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);; return false; } @@ -2385,7 +2386,7 @@ static void do_nocb_deferred_wakeup_timer(struct timer_list *t) { struct rcu_data *rdp = from_timer(rdp, t, nocb_timer); - do_nocb_deferred_wakeup_common(rdp); + do_nocb_deferred_wakeup_common(rdp, RCU_NOCB_WAKE); } /* @@ -2398,8 +2399,8 @@ static bool do_nocb_deferred_wakeup(struct rcu_data *rdp) if (!rdp->nocb_gp_rdp) return false; - if (rcu_nocb_need_deferred_wakeup(rdp->nocb_gp_rdp)) - return do_nocb_deferred_wakeup_common(rdp); + if (rcu_nocb_need_deferred_wakeup(rdp->nocb_gp_rdp, RCU_NOCB_WAKE)) + return do_nocb_deferred_wakeup_common(rdp, RCU_NOCB_WAKE); return false; }