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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 7152CC43144 for ; Tue, 26 Jun 2018 00:33:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C20725C10 for ; Tue, 26 Jun 2018 00:33:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C20725C10 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964916AbeFZAdn (ORCPT ); Mon, 25 Jun 2018 20:33:43 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60244 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755747AbeFZAdT (ORCPT ); Mon, 25 Jun 2018 20:33:19 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w5Q0Sb2K040878 for ; Mon, 25 Jun 2018 20:33:18 -0400 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ju96ubmth-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 25 Jun 2018 20:33:18 -0400 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 25 Jun 2018 20:33:17 -0400 Received: from b01cxnp22035.gho.pok.ibm.com (9.57.198.25) by e17.ny.us.ibm.com (146.89.104.204) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 25 Jun 2018 20:33:10 -0400 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5Q0XAo110420960 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 26 Jun 2018 00:33:10 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AF0F9B2071; Mon, 25 Jun 2018 20:33:04 -0400 (EDT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8F8F7B2067; Mon, 25 Jun 2018 20:33:04 -0400 (EDT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.159]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 25 Jun 2018 20:33:04 -0400 (EDT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id C7C1016CA098; Mon, 25 Jun 2018 17:35:14 -0700 (PDT) From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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 tip/core/rcu 06/27] rcu: Mark task as .need_qs less aggressively Date: Mon, 25 Jun 2018 17:34:52 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180626003448.GA26209@linux.vnet.ibm.com> References: <20180626003448.GA26209@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062600-0040-0000-0000-000004452898 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009255; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052336; UDB=6.00539469; IPR=6.00830262; MB=3.00021856; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-26 00:33:15 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062600-0041-0000-0000-0000084B3E58 Message-Id: <20180626003513.27812-6-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-25_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=871 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806260005 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If any scheduling-clock interrupt interrupts an RCU-preempt read-side critical section, the interrupted task's ->rcu_read_unlock_special.b.need_qs field is set. This causes the outermost rcu_read_unlock() to incur the extra overhead of calling into rcu_read_unlock_special(). This commit reduces that overhead by setting ->rcu_read_unlock_special.b.need_qs only if the grace period has been in effect for more than one second. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index dbfe90191e19..0239cf8a4be6 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -730,6 +730,7 @@ rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, struct rcu_node *rnp) */ static void rcu_preempt_check_callbacks(void) { + struct rcu_state *rsp = &rcu_preempt_state; struct task_struct *t = current; if (t->rcu_read_lock_nesting == 0) { @@ -738,7 +739,9 @@ static void rcu_preempt_check_callbacks(void) } if (t->rcu_read_lock_nesting > 0 && __this_cpu_read(rcu_data_p->core_needs_qs) && - __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm)) + __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm) && + !t->rcu_read_unlock_special.b.need_qs && + time_after(jiffies, rsp->gp_start + HZ)) t->rcu_read_unlock_special.b.need_qs = true; } -- 2.17.1