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 EB9B1C2D0EC for ; Fri, 27 Mar 2020 22:25:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1C922073B for ; Fri, 27 Mar 2020 22:25:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585347955; bh=1nn9QtPMvUtw5J8lfCbvfOGClwyMMAJVbt0kG1bLOmI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zAZVTQVTIIup4xWRaWyYsCyUBe8f8081kINALNwh5IqD1295b3/bdu2yrI5XZaKU8 mNcDqMwdRHb6qBkhVArnXeXHL/W2zkXj1ovHaFZHR5GddAyc61wKbRgLK4pT3rQRDv j63MPfqPjYKvyL9Wllx92uPXQBL1SlU91nppalnE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728069AbgC0WZw (ORCPT ); Fri, 27 Mar 2020 18:25:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:43316 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727876AbgC0WZJ (ORCPT ); Fri, 27 Mar 2020 18:25:09 -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 B29EC21927; Fri, 27 Mar 2020 22:25:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585347908; bh=1nn9QtPMvUtw5J8lfCbvfOGClwyMMAJVbt0kG1bLOmI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wKT67xEcMLAjt1OB+qdmOR3qmOqGzLDsrZ6q8oZPo3npTzGCPnzGwodq8I158OAgi DYeLpTrJXnYwchLpxy1vuVfPE2Z6XQq78pfsaQXHUvqMyYsLK2oazPSSwrcwcoTMPe SAW+tuhDJHYtL408ZyHtWBtJXxgTUwZXFCFljuK0= 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 v3 tip/core/rcu 31/34] rcu-tasks: Add rcu_dynticks_zero_in_eqs() effectiveness statistics Date: Fri, 27 Mar 2020 15:24:53 -0700 Message-Id: <20200327222456.12470-31-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200327222346.GA12082@paulmck-ThinkPad-P72> References: <20200327222346.GA12082@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@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 27d2458..c1a0706 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