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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id q2sm4901973ljp.135.2020.07.03.08.57.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2020 08:57:51 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 3 Jul 2020 17:57:49 +0200 To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrew Morton , Linus Torvalds , GregKroah-Hartmangregkh@linuxfoundation.org, peterz@infradead.org Subject: nr_cpu_ids vs AMD 3970x(32 physical CPUs) Message-ID: <20200703155749.GA6255@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 8898B180D018B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, folk. I have a system based on AMD 3970x CPUs. It has 32 physical cores and 64 threads. It seems that "nr_cpu_ids" variable is not correctly set on latest 5.8-rc3 kernel. Please have a look below on dmesg output: urezki@pc638:~$ sudo dmesg | grep 128 [ 0.000000] IOAPIC[0]: apic_id 128, version 33, address 0xfec00000, GSI 0-23 [ 0.000000] smpboot: Allowing 128 CPUs, 64 hotplug CPUs [ 0.000000] setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:128 nr_node_ids:1 ... [ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=128, Nodes=1 [ 0.000000] rcu: RCU restricting CPUs from NR_CPUS=512 to nr_cpu_ids=128. [ 0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=128 urezki@pc638:~$ For example SLUB thinks that it deals with 128 CPUs in the system what is wrong if i do not miss something. Since nr_cpu_ids is broken(?), thus the "cpu_possible_mask" does not correspond to reality as well. Any thoughts? Thanks! -- Vlad Rezki