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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A071C433F5 for ; Thu, 2 Dec 2021 00:39:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354778AbhLBAnD (ORCPT ); Wed, 1 Dec 2021 19:43:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354680AbhLBAm0 (ORCPT ); Wed, 1 Dec 2021 19:42:26 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10DECC061757; Wed, 1 Dec 2021 16:39:04 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 5B52FCE207A; Thu, 2 Dec 2021 00:39:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81539C53FAD; Thu, 2 Dec 2021 00:39:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638405540; bh=g2AJF18QL/jB1Cgf9DLJpxuqSTHIH94B0ZI5SsV1Oww=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IVS+MlIXycbc4grrybWOEZPw5eaQSLk54Pa92lZlDlpvZp2xWklFK0czYSZPRpzZ1 9hARckfTf4+vxnXHC5Di0aQo+1BR03nmDvFE5+hcDy3vgHJ2ktLcrJbsOsTUxWXuS6 9xEP4tw+V1ouo/6ekzuowpiiFkuCAZUnS0+ZKx6dMts+MsYtmnGArXw02OOZB2TByy A0hw564RyjtPOGuCzpGTrSGiIQs6X/uRH0E5pEN4wI2mRQ9vzVqqgf0QjfNmQ3kVAq iPagex4pc5y/KVERz7Z2Dr4qomHuJSS2oupO32XVfINGryh/01VCrRGg8Q8fP8yhac BZoHzCF5KlazQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 4809F5C1010; Wed, 1 Dec 2021 16:39:00 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" , Martin Lau , Neeraj Upadhyay Subject: [PATCH rcu 03/18] rcu-tasks: Introduce ->percpu_enqueue_shift for dynamic queue selection Date: Wed, 1 Dec 2021 16:38:43 -0800 Message-Id: <20211202003858.3129628-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20211202003826.GA3129369@paulmck-ThinkPad-P17-Gen-1> References: <20211202003826.GA3129369@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit introduces a ->percpu_enqueue_shift field to the rcu_tasks structure, and uses it to shift down the CPU number in order to select a rcu_tasks_percpu structure. This field is currently set to a sufficiently large shift count to always select the CPU-0 instance of the rcu_tasks_percpu structure, and later commits will adjust this. Reported-by: Martin Lau Cc: Neeraj Upadhyay Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 30048db7aa49d..2a5fe3e04b363 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -52,6 +52,7 @@ struct rcu_tasks_percpu { * @postgp_func: This flavor's post-grace-period function (optional). * @call_func: This flavor's call_rcu()-equivalent function. * @rtpcpu: This flavor's rcu_tasks_percpu structure. + * @percpu_enqueue_shift: Shift down CPU ID this much when enqueuing callbacks. * @name: This flavor's textual name. * @kname: This flavor's kthread name. */ @@ -75,6 +76,7 @@ struct rcu_tasks { postgp_func_t postgp_func; call_rcu_func_t call_func; struct rcu_tasks_percpu __percpu *rtpcpu; + int percpu_enqueue_shift; char *name; char *kname; }; @@ -91,6 +93,7 @@ static struct rcu_tasks rt_name = \ .call_func = call, \ .rtpcpu = &rt_name ## __percpu, \ .name = n, \ + .percpu_enqueue_shift = ilog2(CONFIG_NR_CPUS), \ .kname = #rt_name, \ } @@ -169,6 +172,7 @@ static void cblist_init_generic(struct rcu_tasks *rtp) unsigned long flags; raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags); + rtp->percpu_enqueue_shift = ilog2(nr_cpu_ids); for_each_possible_cpu(cpu) { struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); @@ -195,7 +199,8 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, rhp->next = NULL; rhp->func = func; local_irq_save(flags); - rtpcp = per_cpu_ptr(rtp->rtpcpu, 0 /* smp_processor_id() */); + rtpcp = per_cpu_ptr(rtp->rtpcpu, + smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift)); raw_spin_lock(&rtpcp->cbs_pcpu_lock); if (!rtpcp->cbs_tail) { raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled. -- 2.31.1.189.g2e36527f23