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 D69BBC32774 for ; Tue, 23 Aug 2022 07:48:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241194AbiHWHsH (ORCPT ); Tue, 23 Aug 2022 03:48:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57160 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241186AbiHWHsF (ORCPT ); Tue, 23 Aug 2022 03:48:05 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99E4E647FC for ; Tue, 23 Aug 2022 00:48:03 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MBh9M36H9znThn; Tue, 23 Aug 2022 15:45:43 +0800 (CST) Received: from [10.67.102.169] (10.67.102.169) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 23 Aug 2022 15:48:01 +0800 CC: , , , , , , , , , , , , , , , , , , <21cnbao@gmail.com>, , , , , , Subject: Re: [PATCH v7 2/2] sched/fair: Scan cluster before scanning LLC in wake-up path To: Chen Yu References: <20220822073610.27205-1-yangyicong@huawei.com> <20220822073610.27205-3-yangyicong@huawei.com> From: Yicong Yang Message-ID: <53b1fc3c-b6a9-a4cb-433a-c5c6af1d1dac@huawei.com> Date: Tue, 23 Aug 2022 15:48:00 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.169] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500009.china.huawei.com (7.192.105.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/8/23 11:45, Chen Yu wrote: > On 2022-08-22 at 15:36:10 +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. >> >> 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: >> 6.0-rc1 patched >> Hmean 1 351.20 ( 0.00%) 396.45 * 12.88%* >> Hmean 2 700.43 ( 0.00%) 793.76 * 13.32%* >> Hmean 4 1404.42 ( 0.00%) 1583.62 * 12.76%* >> Hmean 8 2833.31 ( 0.00%) 3147.85 * 11.10%* >> Hmean 16 5501.90 ( 0.00%) 6089.89 * 10.69%* >> Hmean 32 10428.59 ( 0.00%) 10619.63 * 1.83%* >> Hmean 64 8223.39 ( 0.00%) 8306.93 * 1.02%* >> Hmean 128 7042.88 ( 0.00%) 7068.03 * 0.36%* >> >> On numa 0-1: >> 6.0-rc1 patched >> Hmean 1 363.06 ( 0.00%) 397.13 * 9.38%* >> Hmean 2 721.68 ( 0.00%) 789.84 * 9.44%* >> Hmean 4 1435.15 ( 0.00%) 1566.01 * 9.12%* >> Hmean 8 2776.17 ( 0.00%) 3007.05 * 8.32%* >> Hmean 16 5471.71 ( 0.00%) 6103.91 * 11.55%* >> Hmean 32 10164.98 ( 0.00%) 11531.81 * 13.45%* >> Hmean 64 17143.28 ( 0.00%) 20078.68 * 17.12%* >> Hmean 128 14552.70 ( 0.00%) 15156.41 * 4.15%* >> Hmean 256 12827.37 ( 0.00%) 13326.86 * 3.89%* >> >> Note neither Kunpeng920 nor x86 Jacobsville supports SMT, so the SMT branch >> in the code has not been tested but it supposed to work. >> >> Suggested-by: Peter Zijlstra >> [https://lore.kernel.org/lkml/Ytfjs+m1kUs0ScSn@worktop.programming.kicks-ass.net] >> Tested-by: Yicong Yang >> Signed-off-by: Barry Song >> Signed-off-by: Yicong Yang >> Reviewed-by: Tim Chen >> --- >> kernel/sched/fair.c | 30 +++++++++++++++++++++++++++--- >> kernel/sched/sched.h | 2 ++ >> kernel/sched/topology.c | 10 ++++++++++ >> 3 files changed, 39 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 914096c5b1ae..6fa77610d0f5 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -6437,6 +6437,30 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool >> } >> } >> >> + if (static_branch_unlikely(&sched_cluster_active)) { >> + struct sched_domain *sdc = rcu_dereference(per_cpu(sd_cluster, target)); >> + >> + if (sdc) { >> + for_each_cpu_wrap(cpu, sched_domain_span(sdc), target + 1) { > Looks good to me. One minor question, why don't we use > cpumask_and(cpus, sched_domain_span(sdc), cpus); >> + if (!cpumask_test_cpu(cpu, cpus)) >> + continue; > so above check can be removed in each loop? Since we'll need to recalculate the mask of rest CPUs to test in the LLC after scanning the cluster CPUs. > Besides may I know what version this patch > is based on? since I failed to apply the patch on v6.0-rc2. Other than that: > It's on 6.0-rc1 when sent but can be cleanly rebased on rc2: yangyicong@ubuntu:~/mainline_linux/linux_sub_workspace$ git log --oneline -3 0079c27ba265 (HEAD -> topost-cls-v7, topost-cls-v6) sched/fair: Scan cluster before scanning LLC in wake-up path 1ecb9e322bd7 sched: Add per_cpu cluster domain info and cpus_share_lowest_cache API 1c23f9e627a7 (tag: v6.0-rc2, origin/master, origin/HEAD, master) Linux 6.0-rc2 So I'm not sure where's the problem... > Reviewed-by: Chen Yu > Thanks! > thanks, > Chenyu >> + >> + if (has_idle_core) { >> + i = select_idle_core(p, cpu, cpus, &idle_cpu); >> + if ((unsigned int)i < nr_cpumask_bits) >> + return i; >> + } else { >> + if (--nr <= 0) >> + return -1; >> + idle_cpu = __select_idle_cpu(cpu, p); >> + if ((unsigned int)idle_cpu < nr_cpumask_bits) >> + return idle_cpu; >> + } >> + } >> + cpumask_andnot(cpus, cpus, sched_domain_span(sdc)); >> + } >> + } > . >