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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 58ECDC3815B for ; Wed, 15 Apr 2020 18:21:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A84220787 for ; Wed, 15 Apr 2020 18:21:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586974906; bh=u9WDPJ9PVhLe00nroezkeAOMPAu5vRYHEOa3AE/9rBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YLB+GovlcGoCpixmHjReEQLa2MVETQSifAczaXFwbmoI218pqBbr0+nETdSez7z3r SR5L5l4VCw5jOzLnntWWp6OzGSecmeY5ijuo/J8Ta1eSWCaqJADuuNt5tWqADSp4JX 3OgBX3piknfEomlzJ0PIN2/wD1tjsR3UaaU9poOY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2441477AbgDOSVn (ORCPT ); Wed, 15 Apr 2020 14:21:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:37886 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2441396AbgDOSTz (ORCPT ); Wed, 15 Apr 2020 14:19:55 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9287E21BE5; Wed, 15 Apr 2020 18:19:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586974794; bh=u9WDPJ9PVhLe00nroezkeAOMPAu5vRYHEOa3AE/9rBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=16G12vWV5otnRrHhYIEMlBGoo7Px1ovnQHIAR4q4+xpG8Jvpx4jsLCI0SbZOJbxtQ te9zxr8S8zNkC7y6P2yt9u6Nj3SL4z1bIG0qOjhRF9LhNWJWsQ3fwvPnDwotmLfi5A EBLUZUB1Q75Jap/4UEGMoCAijkdly4yOiCS0yYdw= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.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" Subject: [PATCH v4 tip/core/rcu 32/38] rcu-tasks: Add rcu_dynticks_zero_in_eqs() effectiveness statistics Date: Wed, 15 Apr 2020 11:19:35 -0700 Message-Id: <20200415181941.11653-32-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200415181856.GA11037@paulmck-ThinkPad-P72> References: <20200415181856.GA11037@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" This commit adds counts of the number of calls and number of successful calls to rcu_dynticks_zero_in_eqs(), which are printed at the end of rcutorture runs and at stall time. This allows evaluation of the effectiveness of rcu_dynticks_zero_in_eqs(). Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 6bd9bfe..b51f19a 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -725,6 +725,11 @@ DECLARE_WAIT_QUEUE_HEAD(trc_wait); // List of holdout tasks. // Record outstanding IPIs to each CPU. No point in sending two... static DEFINE_PER_CPU(bool, trc_ipi_to_cpu); +// The number of detections of task quiescent state relying on +// heavyweight readers executing explicit memory barriers. +unsigned long n_heavy_reader_attempts; +unsigned long n_heavy_reader_updates; + void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace, "RCU Tasks Trace"); @@ -830,9 +835,11 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) // If heavyweight readers are enabled on the remote task, // we can inspect its state despite its currently running. // However, we cannot safely change its state. + n_heavy_reader_attempts++; if (!ofl && // Check for "running" idle tasks on offline CPUs. !rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting)) return false; // No quiescent state, do it the hard way. + n_heavy_reader_updates++; in_qs = true; } else { in_qs = likely(!t->trc_reader_nesting); @@ -1143,9 +1150,11 @@ core_initcall(rcu_spawn_tasks_trace_kthread); static void show_rcu_tasks_trace_gp_kthread(void) { - char buf[32]; + char buf[64]; - sprintf(buf, "N%d", atomic_read(&trc_n_readers_need_end)); + sprintf(buf, "N%d h:%lu/%lu", atomic_read(&trc_n_readers_need_end), + data_race(n_heavy_reader_updates), + data_race(n_heavy_reader_attempts)); show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf); } -- 2.9.5