Unknown NUMA node; performance will be reduced

[Barnes]

Hello,

This is happening in a VM installed from Ubuntu minimal server cloud image 22.04 LTS.
https://cloud-images.ubuntu.com/min...lease/ubuntu-22.04-minimal-cloudimg-amd64.img

pve-manager/7.2-11/b76d3178 (running kernel: 5.15.53-1-pve)
4 node Proxmox ceph cluster, with AMD Epyc.

I have enabled NUMA on VM with two sockets and two cores.
Kernel boot parameter added "memhp_default_state=online"
Kernel 5.15.0-1019-kvm

dmesg |grep NUMA
[ 0.003311] NUMA: Node 0 [mem 0x00000000-0x0009ffff] + [mem 0x00100000-0x1fffffff] -> [mem 0x00000000-0x1fffffff]
[ 0.068890] mempolicy: Enabling automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl
[ 0.174795] pci_bus 0000:00: Unknown NUMA node; performance will be reduced

Full dmesg attached

 

[Barnes]

I have had some more time looking in to this, and it is not visible in dmesg on a Ubuntu 20.04 image and one difference I noticed is one kernel parameter CONFIG_NUMA_KEEP_MEMINFO=y

Ubuntu 20.04
grep NUMA /boot/config-5.4.0-1076-kvm
CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
CONFIG_NUMA_BALANCING=y
CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
CONFIG_NUMA=y
CONFIG_AMD_NUMA=y
CONFIG_X86_64_ACPI_NUMA=y
# CONFIG_NUMA_EMU is not set
CONFIG_USE_PERCPU_NUMA_NODE_ID=y
CONFIG_ACPI_NUMA=y

Ubuntu 22.04
grep NUMA /boot/config-5.15.0-1019-kvm
CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
CONFIG_NUMA_BALANCING=y
CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
CONFIG_NUMA=y
CONFIG_AMD_NUMA=y
CONFIG_X86_64_ACPI_NUMA=y
# CONFIG_NUMA_EMU is not set
CONFIG_USE_PERCPU_NUMA_NODE_ID=y
CONFIG_ACPI_NUMA=y
CONFIG_NUMA_KEEP_MEMINFO=y