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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 C0854C28CF6 for ; Fri, 3 Aug 2018 06:14:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A44921711 for ; Fri, 3 Aug 2018 06:14:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A44921711 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 S1727809AbeHCIJc (ORCPT ); Fri, 3 Aug 2018 04:09:32 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37444 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726833AbeHCIJc (ORCPT ); Fri, 3 Aug 2018 04:09:32 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w736EHZn093247 for ; Fri, 3 Aug 2018 02:14:48 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0b-001b2d01.pphosted.com with ESMTP id 2kmgpu9vj2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 03 Aug 2018 02:14:48 -0400 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 3 Aug 2018 07:14:44 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w736Eh4A37093524 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 3 Aug 2018 06:14:43 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2DDD8AE051; Fri, 3 Aug 2018 09:14:42 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D6FD6AE04D; Fri, 3 Aug 2018 09:14:40 +0100 (BST) Received: from srikart450.in.ibm.com (unknown [9.122.211.85]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 3 Aug 2018 09:14:40 +0100 (BST) From: Srikar Dronamraju To: Ingo Molnar , Peter Zijlstra Cc: LKML , Mel Gorman , Rik van Riel , Srikar Dronamraju , Thomas Gleixner Subject: [PATCH 1/6] sched/numa: Stop multiple tasks from moving to the cpu at the same time Date: Fri, 3 Aug 2018 11:43:56 +0530 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1533276841-16341-1-git-send-email-srikar@linux.vnet.ibm.com> References: <1533276841-16341-1-git-send-email-srikar@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18080306-4275-0000-0000-000002A2F11D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18080306-4276-0000-0000-000037AB0D91 Message-Id: <1533276841-16341-2-git-send-email-srikar@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-03_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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=8.0.1-1807170000 definitions=main-1808030068 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Task migration under numa balancing can happen in parallel. More than one task might choose to migrate to the same cpu at the same time. This can result in - During task swap, choosing a task that was not part of the evaluation. - During task swap, task which just got moved into its preferred node, moving to a completely different node. - During task swap, task failing to move to the preferred node, will have to wait an extra interval for the next migrate opportunity. - During task movement, multiple task movements can cause load imbalance. This problem is more likely if there are more cores per node or more nodes in the system. Use a per run-queue variable to check if numa-balance is active on the run-queue. specjbb2005 / bops/JVM / higher bops are better on 2 Socket/2 Node Intel JVMS Prev Current %Change 4 199709 206350 3.32534 1 330830 319963 -3.28477 on 2 Socket/4 Node Power8 (PowerNV) JVMS Prev Current %Change 8 89011.9 89627.8 0.69193 1 218946 211338 -3.47483 on 2 Socket/2 Node Power9 (PowerNV) JVMS Prev Current %Change 4 180473 186539 3.36117 1 212805 220344 3.54268 on 4 Socket/4 Node Power7 JVMS Prev Current %Change 8 56941.8 56836 -0.185804 1 111686 112970 1.14965 dbench / transactions / higher numbers are better on 2 Socket/2 Node Intel count Min Max Avg Variance %Change 5 12029.8 12124.6 12060.9 34.0076 5 13136.1 13170.2 13150.2 14.7482 9.03166 on 2 Socket/4 Node Power8 (PowerNV) count Min Max Avg Variance %Change 5 4968.51 5006.62 4981.31 13.4151 5 4319.79 4998.19 4836.53 261.109 -2.90646 on 2 Socket/2 Node Power9 (PowerNV) count Min Max Avg Variance %Change 5 9342.92 9381.44 9363.92 12.8587 5 9325.56 9402.7 9362.49 25.9638 -0.0152714 on 4 Socket/4 Node Power7 count Min Max Avg Variance %Change 5 143.4 188.892 170.225 16.9929 5 132.581 191.072 170.554 21.6444 0.193274 Acked-by: Mel Gorman Reviewed-by: Rik van Riel Signed-off-by: Srikar Dronamraju Signed-off-by: Srikar Dronamraju --- Changelog v2->v3: Add comments as requested by Peter. kernel/sched/fair.c | 22 ++++++++++++++++++++++ kernel/sched/sched.h | 1 + 2 files changed, 23 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 309c93f..5cf921a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1514,6 +1514,21 @@ struct task_numa_env { static void task_numa_assign(struct task_numa_env *env, struct task_struct *p, long imp) { + struct rq *rq = cpu_rq(env->dst_cpu); + + /* Bail out if run-queue part of active numa balance. */ + if (xchg(&rq->numa_migrate_on, 1)) + return; + + /* + * Clear previous best_cpu/rq numa-migrate flag, since task now + * found a better cpu to move/swap. + */ + if (env->best_cpu != -1) { + rq = cpu_rq(env->best_cpu); + WRITE_ONCE(rq->numa_migrate_on, 0); + } + if (env->best_task) put_task_struct(env->best_task); if (p) @@ -1569,6 +1584,9 @@ static void task_numa_compare(struct task_numa_env *env, long moveimp = imp; int dist = env->dist; + if (READ_ONCE(dst_rq->numa_migrate_on)) + return; + rcu_read_lock(); cur = task_rcu_dereference(&dst_rq->curr); if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) @@ -1710,6 +1728,7 @@ static int task_numa_migrate(struct task_struct *p) .best_cpu = -1, }; struct sched_domain *sd; + struct rq *best_rq; unsigned long taskweight, groupweight; int nid, ret, dist; long taskimp, groupimp; @@ -1811,14 +1830,17 @@ static int task_numa_migrate(struct task_struct *p) */ p->numa_scan_period = task_scan_start(p); + best_rq = cpu_rq(env.best_cpu); if (env.best_task == NULL) { ret = migrate_task_to(p, env.best_cpu); + WRITE_ONCE(best_rq->numa_migrate_on, 0); if (ret != 0) trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); return ret; } ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu); + WRITE_ONCE(best_rq->numa_migrate_on, 0); if (ret != 0) trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 4a2e8ca..0b91612 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -783,6 +783,7 @@ struct rq { #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; unsigned int nr_preferred_running; + unsigned int numa_migrate_on; #endif #define CPU_LOAD_IDX_MAX 5 unsigned long cpu_load[CPU_LOAD_IDX_MAX]; -- 1.8.3.1