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 13BDAC32772 for ; Tue, 23 Aug 2022 16:36:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244904AbiHWQgR (ORCPT ); Tue, 23 Aug 2022 12:36:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245289AbiHWQfq (ORCPT ); Tue, 23 Aug 2022 12:35:46 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2519D41A0 for ; Tue, 23 Aug 2022 06:06:17 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MBqDn22Y4zGplg; Tue, 23 Aug 2022 21:04:09 +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 21:05:48 +0800 CC: , , , , , , <21cnbao@gmail.com>, , , Subject: Re: [PATCH] arch_topology: Make cluster topology span at least SMT CPUs To: Ionela Voinescu References: <20220823073044.58697-1-yangyicong@huawei.com> From: Yicong Yang Message-ID: Date: Tue, 23 Aug 2022 21:05:47 +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: dggems701-chm.china.huawei.com (10.3.19.178) 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 16:06, Ionela Voinescu wrote: > Hi Yicong, > > On Tuesday 23 Aug 2022 at 15:30:44 (+0800), Yicong Yang wrote: >> From: Yicong Yang >> >> Currently cpu_clustergroup_mask() will return CPU mask if cluster span >> more or the same CPUs as cpu_coregroup_mask(). This will result topology >> borken on non-Cluster SMT machines. > > Might be worth adding here:.. "when building with CONFIG_SCHED_CLUSTER=y" > will add this qualifier. thanks. >> > > I thought I had covered this case, but I think I had considered LLC > spanning more than one core (tested on TX2 as well). > > So you'd only hit this if LLC and cluster level span the same cores (a > single core in this case, for non-cluster), in the presence of SMT. > Not sure I understand it correctly but in the below case I think the LLC may span the same core with socket? > Reviewed-by: Ionela Voinescu > > Many thanks, > Ionela. > >> Test with: >> qemu-system-aarch64 -enable-kvm -machine virt \ >> -net none \ >> -cpu host \ >> -bios ./QEMU_EFI.fd \ >> -m 2G \ >> -smp 48,sockets=2,cores=12,threads=2 \ >> -kernel $Image \ >> -initrd $Rootfs \ >> -nographic >> -append "rdinit=init console=ttyAMA0 sched_verbose loglevel=8" >> >> We'll get below error: >> [ 3.084568] BUG: arch topology borken >> [ 3.084570] the SMT domain not a subset of the CLS domain >> >> Since cluster is a level higher than SMT, fix this by making cluster >> spans at least SMT CPUs. >> >> Cc: Sudeep Holla >> Cc: Vincent Guittot >> Cc: Ionela Voinescu >> Fixes: bfcc4397435d ("arch_topology: Limit span of cpu_clustergroup_mask()") >> Signed-off-by: Yicong Yang >> --- >> drivers/base/arch_topology.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c >> index 0424b59b695e..0056a1273275 100644 >> --- a/drivers/base/arch_topology.c >> +++ b/drivers/base/arch_topology.c >> @@ -724,7 +724,7 @@ const struct cpumask *cpu_clustergroup_mask(int cpu) >> */ >> if (cpumask_subset(cpu_coregroup_mask(cpu), >> &cpu_topology[cpu].cluster_sibling)) >> - return get_cpu_mask(cpu); >> + return cpu_smt_mask(cpu); >> >> return &cpu_topology[cpu].cluster_sibling; >> } >> -- >> 2.24.0 >> > > . >