> > > > 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. > I suspect that DEFINE_PER_CPU variables can be twice as big, but i have not checked it actually. So, if the code needs to identify real number of CPUs it can be a challenge :) Thanks. -- Vlad Rezki
