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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9556FC6FA8E for ; Sat, 25 Feb 2023 00:06:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pVi4o-00048R-2s; Fri, 24 Feb 2023 19:06:10 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pVi4m-00042s-G3 for qemu-devel@nongnu.org; Fri, 24 Feb 2023 19:06:08 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pVi4h-0007Or-JC for qemu-devel@nongnu.org; Fri, 24 Feb 2023 19:06:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677283561; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wJrR/b3T+mJBBQo5YN6sUaiHLTKTzqYvLAXS02lkwSo=; b=gZcxoFmXaICsD6cbMx9ABGu6OUMGyWqU4CEjK/fhTvE6ooOqV6x6hV++HIan+5Y76NgLQQ 5yzrS77u92urjyhrz+5eGuYCQcu81jq7EnTwzaLD02botIp0McbWCkrLpRvfXkrQ1VEhOo WuqQ87mF4i+ppfI5Z03OFgOPQ6yWv9U= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-519-m2ia8WHWPTixnBmC4wRt0w-1; Fri, 24 Feb 2023 19:05:57 -0500 X-MC-Unique: m2ia8WHWPTixnBmC4wRt0w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4506E29A9CA8; Sat, 25 Feb 2023 00:05:56 +0000 (UTC) Received: from [10.64.54.20] (vpn2-54-20.bne.redhat.com [10.64.54.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BF28B2026D4B; Sat, 25 Feb 2023 00:05:46 +0000 (UTC) Subject: Re: [PATCH v2 0/4] NUMA: Apply socket-NUMA-node boundary for aarch64 and RiscV machines To: Igor Mammedov Cc: Daniel Henrique Barboza , qemu-arm@nongnu.org, qemu-devel@nongnu.org, qemu-riscv@nongnu.org, rad@semihalf.com, peter.maydell@linaro.org, quic_llindhol@quicinc.com, eduardo@habkost.net, marcel.apfelbaum@gmail.com, philmd@linaro.org, wangyanan55@huawei.com, palmer@dabbelt.com, alistair.francis@wdc.com, bin.meng@windriver.com, thuth@redhat.com, lvivier@redhat.com, pbonzini@redhat.com, yihyu@redhat.com, shan.gavin@gmail.com, =?UTF-8?B?TWljaGFsIFByw612b3puw61r?= References: <20230223081401.248835-1-gshan@redhat.com> <2d37d157-12a1-07aa-4c70-974ac1503283@ventanamicro.com> <11e958b1-4763-f710-fe02-832cfd559e7b@ventanamicro.com> <9e8523a9-9059-e3a0-e32e-414f83e06a6f@redhat.com> <20230224152035.6edfa832@imammedo.users.ipa.redhat.com> From: Gavin Shan Message-ID: <7638e643-7a05-808c-ec47-c29db1c5d75f@redhat.com> Date: Sat, 25 Feb 2023 11:05:42 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20230224152035.6edfa832@imammedo.users.ipa.redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.094, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Gavin Shan Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2/25/23 1:20 AM, Igor Mammedov wrote: > On Fri, 24 Feb 2023 21:16:39 +1100 > Gavin Shan wrote: > >> On 2/24/23 8:26 PM, Daniel Henrique Barboza wrote: >>> On 2/24/23 04:09, Gavin Shan wrote: >>>> On 2/24/23 12:18 AM, Daniel Henrique Barboza wrote: >>>>> On 2/23/23 05:13, Gavin Shan wrote: >>>>>> For arm64 and RiscV architecture, the driver (/base/arch_topology.c) is >>>>>> used to populate the CPU topology in the Linux guest. It's required that >>>>>> the CPUs in one socket can't span mutiple NUMA nodes. Otherwise, the Linux >>>>>> scheduling domain can't be sorted out, as the following warning message >>>>>> indicates. To avoid the unexpected confusion, this series attempts to >>>>>> rejects such kind of insane configurations. >>>>>> >>>>>>     -smp 6,maxcpus=6,sockets=2,clusters=1,cores=3,threads=1 \ >>>>>>     -numa node,nodeid=0,cpus=0-1,memdev=ram0                \ >>>>>>     -numa node,nodeid=1,cpus=2-3,memdev=ram1                \ >>>>>>     -numa node,nodeid=2,cpus=4-5,memdev=ram2                \ >>>>> >>>>> >>>>> And why is this a QEMU problem? This doesn't hurt ACPI. >>>>> >>>>> Also, this restriction impacts breaks ARM guests in the wild that are running >>>>> non-Linux OSes. I don't see why we should impact use cases that has nothing to >>>>> do with Linux Kernel feelings about sockets - NUMA nodes exclusivity. >>>>> >>>> >>>> With above configuration, CPU-0/1/2 are put into socket-0-cluster-0 while CPU-3/4/5 >>>> are put into socket-1-cluster-0, meaning CPU-2/3 belong to different socket and >>>> cluster. However, CPU-2/3 are associated with NUMA node-1. In summary, multiple >>>> CPUs in different clusters and sockets have been associated with one NUMA node. >>>> >>>> If I'm correct, the configuration isn't sensible in a baremetal environment and >>>> same Linux kernel is supposed to work well for baremetal and virtualized machine. >>>> So I think QEMU needs to emulate the topology as much as we can to match with the >>>> baremetal environment. It's the reason why I think it's a QEMU problem even it >>>> doesn't hurt ACPI. As I said in the reply to Daniel P. Berrangé >>>> in another thread, we may need to gurantee that the CPUs in one cluster can't be >>>> split to multiple NUMA nodes, which matches with the baremetal environment, as I >>>> can understand. >>>> >>>> Right, the restriction to have socket-NUMA-node or cluster-NUMA-node boundary will >>>> definitely break the configurations running in the wild. >>> >>> >>> What about a warning? If the user attempts to use an exotic NUMA configuration >>> like the one you mentioned we can print something like: >>> >>> "Warning: NUMA topologies where a socket belongs to multiple NUMA nodes can cause OSes like Linux to misbehave" >>> >>> This would inform the user what might be going wrong in case Linux is crashing/error >>> out on them and then the user is free to fix their topology (or the kernel). And >>> at the same time we wouldn't break existing stuff that happens to be working. >>> >>> >> >> Yes, I think a warning message is more appropriate, so that users can fix their >> irregular configurations and the existing configurations aren't disconnected. >> It would be nice to get the agreements from Daniel P. Berrangé and Drew, before >> I'm going to change the code and post next revision. > > Honestly you (and libvirt as far as I recall) are using legacy options > to assign cpus to numa nodes. > With '-numa node,nodeid=0,cpus=0-1' you can't really be sure what/where > in topology those cpus are. > What you can do is to use '-numa cpu,...' option to assign socket/core/... > to numa node, ex: > "-numa cpu,node-id=1,socket-id=0 " or > "-numa cpu,node-id=0,socket-id=1,core-id=0 " or > "-numa cpu,node-id=0,socket-id=1,core-id=1,thread-id=0 > to get your desired mapping. > > The problem that's so far was stopping the later adoption by libvirt (Michal CCed) > is that values used by it are machine specific and to do it properly, for a concrete > '-M x -smp ...' at least for the first time qemu should be started with- > -preconfig option and then user should query possible cpus for those values > and assign them to numa nodes via QMP. > The issue isn't related to the legacy or modern way to configure CPU-to-NUMA association. Note that qtests/numa-test also use the legacy way. For example, the issue can be triggered with the following command lines where the modern configuration is used: /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \ -accel kvm -machine virt,gic-version=host \ -cpu host -smp 6,sockets=2,clusters=1,cores=3,threads=1 \ -m 768M,slots=16,maxmem=64G \ -object memory-backend-ram,id=mem0,size=256M \ -object memory-backend-ram,id=mem1,size=256M \ -object memory-backend-ram,id=mem2,size=256M \ -numa node,nodeid=0,memdev=mem0 \ -numa node,nodeid=1,memdev=mem1 \ -numa node,nodeid=2,memdev=mem2 \ -numa cpu,node-id=0,socket-id=0,cluster-id=0,core-id=0,thread-id=0 \ -numa cpu,node-id=0,socket-id=0,cluster-id=0,core-id=1,thread-id=0 \ -numa cpu,node-id=1,socket-id=0,cluster-id=0,core-id=2,thread-id=0 \ -numa cpu,node-id=1,socket-id=1,cluster-id=0,core-id=0,thread-id=0 \ -numa cpu,node-id=2,socket-id=1,cluster-id=0,core-id=1,thread-id=0 \ -numa cpu,node-id=2,socket-id=1,cluster-id=0,core-id=2,thread-id=0 : : [ 0.022260] =============== sched_init_domains =================== [ 0.022263] CPU-0: 36,56,0,-1 thread=0 core=0-2 cluster=0-2 llc=0 [ 0.022267] CPU-1: 36,56,1,-1 thread=1 core=0-2 cluster=0-2 llc=1 [ 0.022269] CPU-2: 36,56,2,-1 thread=2 core=0-2 cluster=0-2 llc=2 [ 0.022270] CPU-3: 136,156,3,-1 thread=3 core=3-5 cluster=3-5 llc=3 [ 0.022272] CPU-4: 136,156,4,-1 thread=4 core=3-5 cluster=3-5 llc=4 [ 0.022273] CPU-5: 136,156,5,-1 thread=5 core=3-5 cluster=3-5 llc=5 [ 0.022275] CPU-0: SMT=0 CLUSTER=0 MULTICORE=0-2 CPUMASK=0-1 0-1 [ 0.022277] CPU-1: SMT=1 CLUSTER=1 MULTICORE=0-2 CPUMASK=0-1 0-1 [ 0.022279] CPU-2: SMT=2 CLUSTER=0-2 MULTICORE=2-3 CPUMASK=2-3 2-3 [ 0.022281] CPU-3: SMT=3 CLUSTER=3-5 MULTICORE=2-3 CPUMASK=2-3 2-3 [ 0.022283] CPU-4: SMT=4 CLUSTER=4 MULTICORE=3-5 CPUMASK=4-5 4-5 [ 0.022284] CPU-5: SMT=5 CLUSTER=5 MULTICORE=3-5 CPUMASK=4-5 4-5 [ 0.022314] build_sched_domains: CPU-0 level-SMT [ 0.022317] build_sched_domains: CPU-0 level-CLS [ 0.022318] topology_span_sane: CPU-0 0 vs CPU-2 0-2 [ 0.022322] ------------[ cut here ]------------ [ 0.022323] WARNING: CPU: 0 PID: 1 at kernel/sched/topology.c:2275 build_sched_domains+0x135c/0x1660 : > btw: on x86 we also allow 'insane' configuration incl. those that do not > exist on baremetal and do not warn about it anyone (i.e. it's user's > responsibility to provide topology that specific guest OS could handle, > aka it's not QEMU business but upper layers). (I do occasionally try > introduce stricter checks in that are, but that gets push back more > often that not). > > I'd do check only in case of a specific board where mapping is fixed > in specs of emulated machine, otherwise I wouldn't bother. > Right, x86 can handle the irregular configuration well and we didn't find any triggered warning messages there. As the subject indicates, it's a ARM64 or riscv specific issue. Unfortunately, I failed to find the requirement, socket-to-NUMA-node or cluster-to-NUMA-node 1:1 mapping from specs. However, it's not sensible to split CPUs in one cluster to multiple NUMA nodes in a (ARM64 or RISCv) baremetal environment. QEMU needs to emulate the environment close to the baremetal machine if we can. In summary, a warning message when multiple CPUs in one cluster are split to multiple NUMA nodes, as Daniel suggested, sounds reasonable to me. Please let me know your thoughts, Igor :) Thanks, Gavin