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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B0E4C433EF for ; Fri, 28 Jan 2022 07:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242647AbiA1HO2 (ORCPT ); Fri, 28 Jan 2022 02:14:28 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50456 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230226AbiA1HO1 (ORCPT ); Fri, 28 Jan 2022 02:14:27 -0500 Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 20S46DEL038220; Fri, 28 Jan 2022 07:13:49 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : reply-to : references : mime-version : content-type : in-reply-to; s=pp1; bh=OCcByMJ7JRwI3Zhq3AaB9P9tpF9uLjL1wO7PO/3K0h4=; b=FSOYwqzhGK4etDa0ZyjSP1vWkyENL6ZmQ9BRreY0qgM6YQevh3cgXLwiYXXx65XWEKQ/ 9KcsjN20LxN//C3tTPN8dxb3hrVOvsBUWxzvr2EiK/aCSvUI1wmdnEFlVQ3XA5Zb7oOk y7XTRz8ifus7Fcgx7EQjWKyaSCcTF0IXOKzc0039YhfjyPajnQzuhYTeySMP5uCix8Sd +FdWSFHOqc+CNbEzGdsUkAAEmwZRqeMseZkoEumBioPEvO0h8x4lI1zuyrWTrEN/kzqa Lpam+WyYhSRZEfquO9R3wiPyh9+GguHa4q/suRV4HGTSbVJfpwiIu7086IUh8gKBt8XA cQ== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3dv41wf51a-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Jan 2022 07:13:48 +0000 Received: from m0127361.ppops.net (m0127361.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 20S7BRF6005914; Fri, 28 Jan 2022 07:13:48 GMT Received: from ppma01fra.de.ibm.com (46.49.7a9f.ip4.static.sl-reverse.com [159.122.73.70]) by mx0a-001b2d01.pphosted.com with ESMTP id 3dv41wf50u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Jan 2022 07:13:48 +0000 Received: from pps.filterd (ppma01fra.de.ibm.com [127.0.0.1]) by ppma01fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 20S797VC008788; Fri, 28 Jan 2022 07:13:46 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma01fra.de.ibm.com with ESMTP id 3dr9ja4a53-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Jan 2022 07:13:46 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 20S7Dh1b34144596 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 28 Jan 2022 07:13:43 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1E41A4C04A; Fri, 28 Jan 2022 07:13:43 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9B1234C040; Fri, 28 Jan 2022 07:13:38 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Fri, 28 Jan 2022 07:13:38 +0000 (GMT) Date: Fri, 28 Jan 2022 12:43:37 +0530 From: Srikar Dronamraju To: Barry Song <21cnbao@gmail.com> Cc: "Gautham R. Shenoy" , Yicong Yang , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Tim Chen , LKML , LAK , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , prime.zeng@huawei.com, Jonathan Cameron , ego@linux.vnet.ibm.com, Linuxarm , Barry Song , Guodong Xu Subject: Re: [PATCH v2 2/2] sched/fair: Scan cluster before scanning LLC in wake-up path Message-ID: <20220128071337.GC618915@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20220126080947.4529-1-yangyicong@hisilicon.com> <20220126080947.4529-3-yangyicong@hisilicon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: MihSKkaR4n9UlESlqiqQw5T2gT1h12LE X-Proofpoint-GUID: 3XBkUE1canLGIGQVs5aoEcwUKJ0n_XSv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-27_06,2022-01-27_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 phishscore=0 mlxlogscore=999 spamscore=0 malwarescore=0 impostorscore=0 clxscore=1011 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2201280043 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Barry Song <21cnbao@gmail.com> [2022-01-28 09:21:08]: > On Fri, Jan 28, 2022 at 4:41 AM Gautham R. Shenoy > wrote: > > > > On Wed, Jan 26, 2022 at 04:09:47PM +0800, Yicong Yang wrote: > > > From: Barry Song > > > > > > For platforms having clusters like Kunpeng920, CPUs within the same > > > cluster have lower latency when synchronizing and accessing shared > > > resources like cache. Thus, this patch tries to find an idle cpu > > > within the cluster of the target CPU before scanning the whole LLC > > > to gain lower latency. > > > > > > Note neither Kunpeng920 nor x86 Jacobsville supports SMT, so this > > > patch doesn't consider SMT for this moment. > > > > > > Testing has been done on Kunpeng920 by pinning tasks to one numa > > > and two numa. On Kunpeng920, Each numa has 8 clusters and each > > > cluster has 4 CPUs. > > > > > > With this patch, We noticed enhancement on tbench within one > > > numa or cross two numa. > > > > > > On numa 0: > > > 5.17-rc1 patched > > > Hmean 1 324.73 ( 0.00%) 378.01 * 16.41%* > > > Hmean 2 645.36 ( 0.00%) 754.63 * 16.93%* > > > Hmean 4 1302.09 ( 0.00%) 1507.54 * 15.78%* > > > Hmean 8 2612.03 ( 0.00%) 2982.57 * 14.19%* > > > Hmean 16 5307.12 ( 0.00%) 5886.66 * 10.92%* > > > Hmean 32 9354.22 ( 0.00%) 9908.13 * 5.92%* > > > Hmean 64 7240.35 ( 0.00%) 7278.78 * 0.53%* > > > Hmean 128 6186.40 ( 0.00%) 6187.85 ( 0.02%) > > > > > > On numa 0-1: > > > 5.17-rc1 patched > > > Hmean 1 320.01 ( 0.00%) 378.44 * 18.26%* > > > Hmean 2 643.85 ( 0.00%) 752.52 * 16.88%* > > > Hmean 4 1287.36 ( 0.00%) 1505.62 * 16.95%* > > > Hmean 8 2564.60 ( 0.00%) 2955.29 * 15.23%* > > > Hmean 16 5195.69 ( 0.00%) 5814.74 * 11.91%* > > > Hmean 32 9769.16 ( 0.00%) 10872.63 * 11.30%* > > > Hmean 64 15952.50 ( 0.00%) 17281.98 * 8.33%* > > > Hmean 128 13113.77 ( 0.00%) 13895.20 * 5.96%* > > > Hmean 256 10997.59 ( 0.00%) 11244.69 * 2.25%* > > > Hmean 512 14623.60 ( 0.00%) 15526.25 * 6.17%* > > > > > > This will also help to improve the MySQL. With MySQL server > > > running on numa 0 and client running on numa 1, both QPS and > > > latency is imporved on read-write case: > > > 5.17-rc1 patched > > > QPS-16threads 143333.2633 145077.4033(+1.22%) > > > QPS-24threads 195085.9367 202719.6133(+3.91%) > > > QPS-32threads 241165.6867 249020.74(+3.26%) > > > QPS-64threads 244586.8433 253387.7567(+3.60%) > > > avg-lat-16threads 2.23 2.19(+1.19%) > > > avg-lat-24threads 2.46 2.36(+3.79%) > > > avg-lat-36threads 2.66 2.57(+3.26%) > > > avg-lat-64threads 5.23 5.05(+3.44%) > > > > > > Tested-by: Yicong Yang > > > Signed-off-by: Barry Song > > > Signed-off-by: Yicong Yang > > > --- > > > kernel/sched/fair.c | 46 +++++++++++++++++++++++++++++++++++++++++---- > > > 1 file changed, 42 insertions(+), 4 deletions(-) > > > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > > index 5146163bfabb..2f84a933aedd 100644 > > > --- a/kernel/sched/fair.c > > > +++ b/kernel/sched/fair.c > > > @@ -6262,12 +6262,46 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd > > > > > > #endif /* CONFIG_SCHED_SMT */ > > > > > > +#ifdef CONFIG_SCHED_CLUSTER > > > +/* > > > + * Scan the cluster domain for idle CPUs and clear cluster cpumask after scanning > > > + */ > > > +static inline int scan_cluster(struct task_struct *p, int prev_cpu, int target) > > > +{ > > > + struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); > > > + struct sched_domain *sd = rcu_dereference(per_cpu(sd_cluster, target)); > > > + int cpu, idle_cpu; > > > + > > > + /* TODO: Support SMT case while a machine with both cluster and SMT born */ > > > + if (!sched_smt_active() && sd) { > > > + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) { > > > + idle_cpu = __select_idle_cpu(cpu, p); > > > + if ((unsigned int)idle_cpu < nr_cpumask_bits) > > > + return idle_cpu; > > > + } > > > + > > > + /* Don't ping-pong tasks in and out cluster frequently */ > > > + if (cpus_share_resources(target, prev_cpu)) > > > + return target; > > > > We reach here when there aren't any idle CPUs within the > > cluster. However there might be idle CPUs in the MC domain. Is a busy > > @target preferable to a potentially idle CPU within the larger domain > > ? > > Hi Gautham, > Hi Barry, > My benchmark showed some performance regression while load was medium or above > if we grabbed idle cpu in and out the cluster. it turned out the > regression disappeared if > we blocked the ping-pong. so the logic here is that if we have scanned > and found an > idle cpu within the cluster before, we don't let the task jumping back > and forth frequently > as cache synchronization is higher cost. but the code still allows > scanning out of the cluster > if we haven't packed waker and wakee together yet. > Like what Gautham said, should we choose the same cluster if we find that there are no idle-cpus in the LLC? This way we avoid ping-pong if there are no idle-cpus but we still pick an idle-cpu to a busy cpu? > it might not be a universal win in all kinds of workload. we saw > tbench, mysql benefit from > the whole change. but pgbench seems not always. so we are still on the > way to make possible > further tuning here. > > > > > > > -- > > Thanks and Regards > > gautham. > > Thanks > Barry -- Thanks and Regards Srikar Dronamraju