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 E21F9C43142 for ; Mon, 25 Jun 2018 22:45:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D8FA2623A for ; Mon, 25 Jun 2018 22:45:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D8FA2623A 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 S934763AbeFYWpV (ORCPT ); Mon, 25 Jun 2018 18:45:21 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:45632 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934277AbeFYWlf (ORCPT ); Mon, 25 Jun 2018 18:41:35 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w5PMRJ2V133181 for ; Mon, 25 Jun 2018 18:41:35 -0400 Received: from e11.ny.us.ibm.com (e11.ny.us.ibm.com [129.33.205.201]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ju96trcpy-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 25 Jun 2018 18:41:35 -0400 Received: from localhost by e11.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 25 Jun 2018 18:41:34 -0400 Received: from b01cxnp22033.gho.pok.ibm.com (9.57.198.23) by e11.ny.us.ibm.com (146.89.104.198) 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 18:41:29 -0400 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5PMfSf83801458 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 25 Jun 2018 22:41:28 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A25C9B2066; Mon, 25 Jun 2018 18:41:23 -0400 (EDT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 82497B2064; Mon, 25 Jun 2018 18:41:23 -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 18:41:23 -0400 (EDT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id CD01816CA093; Mon, 25 Jun 2018 15:43:33 -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 1/2] rcu: Make expedited grace period use direct call on last leaf Date: Mon, 25 Jun 2018 15:43:31 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180625224308.GA10064@linux.vnet.ibm.com> References: <20180625224308.GA10064@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062522-2213-0000-0000-000002BFD800 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009255; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052299; UDB=6.00539447; IPR=6.00830224; MB=3.00021855; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-25 22:41:33 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062522-2214-0000-0000-00005A9B68D5 Message-Id: <20180625224332.10596-1-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=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806250253 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During expedited grace-period initialization, a work item is scheduled for each leaf rcu_node structure. However, that initialization code is itself (normally) executing from a workqueue, so one of the leaf rcu_node structures could just as well be handled by that pre-existing workqueue, and with less overhead. This commit therefore uses a shiny new rcu_is_leaf_node() macro to execute the last leaf rcu_node structure's initialization directly from the pre-existing workqueue. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 3 +++ kernel/rcu/tree_exp.h | 5 +++-- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 40cea6735c2d..db0870acfdff 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -276,6 +276,9 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) /* Is this rcu_node a leaf? */ #define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1) +/* Is this rcu_node the last leaf? */ +#define rcu_is_last_leaf_node(rsp, rnp) ((rnp) == &(rsp)->node[rcu_num_nodes - 1]) + /* * Do a full breadth-first scan of the rcu_node structures for the * specified rcu_state structure. diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index d40708e8c5d6..c6385ee1af65 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -486,8 +486,9 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, rnp->rew.rew_func = func; rnp->rew.rew_rsp = rsp; if (!READ_ONCE(rcu_par_gp_wq) || - rcu_scheduler_active != RCU_SCHEDULER_RUNNING) { - /* No workqueues yet. */ + rcu_scheduler_active != RCU_SCHEDULER_RUNNING || + rcu_is_last_leaf_node(rsp, rnp)) { + /* No workqueues yet or last leaf, do direct call. */ sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work); continue; } -- 2.17.1