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 315EFC32789 for ; Tue, 23 Aug 2022 19:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234146AbiHWTQo (ORCPT ); Tue, 23 Aug 2022 15:16:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230059AbiHWTQW (ORCPT ); Tue, 23 Aug 2022 15:16:22 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A646A9CCDE for ; Tue, 23 Aug 2022 10:53:26 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2574B113E; Tue, 23 Aug 2022 10:53:29 -0700 (PDT) Received: from localhost (ionvoi01-desktop.cambridge.arm.com [10.1.196.65]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0993D3F718; Tue, 23 Aug 2022 10:53:24 -0700 (PDT) Date: Tue, 23 Aug 2022 18:53:23 +0100 From: Ionela Voinescu To: Yicong Yang Cc: yangyicong@hisilicon.com, sudeep.holla@arm.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, rafael@kernel.org, 21cnbao@gmail.com, jonathan.cameron@huawei.com, linuxarm@huawei.com, prime.zeng@huawei.com Subject: Re: [PATCH] arch_topology: Make cluster topology span at least SMT CPUs Message-ID: References: <20220823073044.58697-1-yangyicong@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tuesday 23 Aug 2022 at 21:05:47 (+0800), Yicong Yang wrote: > 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? Ah, I've jumped to conclusions based on the "non-cluster" mention. Does "non-cluster" just mean that there's no intermediary "cluster" grouping of CPUs between core and LLC? How does the PPTT table look like, by the way? Thanks, Ionela. > > > 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 > >> > > > > . > >