Am Fr., 3. Juli 2020 um 17:58 Uhr schrieb Uladzislau Rezki <urezki@xxxxxxxxx>: > > Hello, folk. Hello, > > 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: > > <snip> > 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:~$ > <snip> > > 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? This is not a 5.8-rc3 problem. Almost all AMD CPUs and APUs are looking like this. The only CPUs I own are getting that right is a dual EPYC box, everything else is broken regarding the right C/T & socket(s) count, and that probably bc is using NUAM code to have the info. I reported that a while back and no-one ever cared. There is even a comment in the hotplug code saying setting the wrong CPU count is a waste of resources. I have a 2200G is reporting 48Cores. AMD Ryzen 7 3750H reporting twice the cores and twice the socket. ... [ 0.040578] smpboot: Allowing 16 CPUs, 8 hotplug CPUs ... [ 0.382122] smpboot: Max logical packages: 2 .. I boot all the boxes restricting the cores to the correct count on the command line. Wasted resource or not, this is still a bug IMO. Best Regards, Gabriel C
