Re: [libvirt-users] NUMA issues on virtualized hosts

Hello, I have cluster with AMD EPYC 7351 cpu. Two CPUs per node. I have performance 8-NUMA configuration: This is from hypervizor: [root@hde10 ~]# lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 64 On-line CPU(s) list: 0-63 Thread(s) per core: 2 Core(s) per socket: 16 Socket(s): 2 NUMA node(s): 8 Vendor ID: AuthenticAMD CPU family: 23 Model: 1 Model name: AMD EPYC 7351 16-Core Processor Stepping: 2 CPU MHz: 1800.000 CPU max MHz: 2400.0000 CPU min MHz: 1200.0000 BogoMIPS: 4800.05 Virtualization: AMD-V L1d cache: 32K L1i cache: 64K L2 cache: 512K L3 cache: 8192K NUMA node0 CPU(s): 0-3,32-35 NUMA node1 CPU(s): 4-7,36-39 NUMA node2 CPU(s): 8-11,40-43 NUMA node3 CPU(s): 12-15,44-47 NUMA node4 CPU(s): 16-19,48-51 NUMA node5 CPU(s): 20-23,52-55 NUMA node6 CPU(s): 24-27,56-59 NUMA node7 CPU(s): 28-31,60-63 I'm running one big virtual on this hypervizor - almost whole memory + all physical CPUs. This is what I'm seeing inside: root@zenon10:~# lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 32 On-line CPU(s) list: 0-31 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 8 NUMA node(s): 8 Vendor ID: AuthenticAMD CPU family: 23 Model: 1 Model name: AMD EPYC 7351 16-Core Processor Stepping: 2 CPU MHz: 2400.000 BogoMIPS: 4800.00 Virtualization: AMD-V Hypervisor vendor: KVM Virtualization type: full L1d cache: 64K L1i cache: 64K L2 cache: 512K NUMA node0 CPU(s): 0-3 NUMA node1 CPU(s): 4-7 NUMA node2 CPU(s): 8-11 NUMA node3 CPU(s): 12-15 NUMA node4 CPU(s): 16-19 NUMA node5 CPU(s): 20-23 NUMA node6 CPU(s): 24-27 NUMA node7 CPU(s): 28-31 This is virtual node configuration: (i tried different numatune settings but it was still the same) <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> <name>one-55782</name> <vcpu><![CDATA[32]]></vcpu> <cputune> <shares>32768</shares> </cputune> <memory>507904000</memory> <os> <type arch='x86_64'>hvm</type> </os> <devices> <emulator><![CDATA[/usr/bin/kvm]]></emulator> <disk type='file' device='disk'> <source file='/opt/opennebula/var/datastores/108/55782/disk.0'/> <target dev='vda'/> <driver name='qemu' type='qcow2' cache='unsafe'/> </disk> <disk type='file' device='disk'> <source file='/opt/opennebula/var/datastores/108/55782/disk.1'/> <target dev='vdc'/> <driver name='qemu' type='raw' cache='unsafe'/> </disk> <disk type='file' device='disk'> <source file='/opt/opennebula/var/datastores/108/55782/disk.2'/> <target dev='vdd'/> <driver name='qemu' type='raw' cache='unsafe'/> </disk> <disk type='file' device='disk'> <source file='/opt/opennebula/var/datastores/108/55782/disk.3'/> <target dev='vde'/> <driver name='qemu' type='raw' cache='unsafe'/> </disk> <disk type='file' device='cdrom'> <source file='/opt/opennebula/var/datastores/108/55782/disk.4'/> <target dev='vdb'/> <readonly/> <driver name='qemu' type='raw'/> </disk> <interface type='bridge'> <source bridge='br0'/> <mac address='02:00:93:fb:3b:78'/> <target dev='one-55782-0'/> <model type='virtio'/> <filterref filter='no-arp-mac-spoofing'> <parameter name='IP' value='147.251.59.120'/> </filterref> </interface> </devices> <features> <pae/> <acpi/> </features> <!-- RAW data follows: --> <cpu mode='host-passthrough'><topology sockets='8' cores='4' threads='1'/><numa><cell cpus='0-3' memory='62000000' /><cell cpus='4-7' memory='62000000' /><cell cpus='8-11' memory='62000000' /><cell cpus='12-15' memory='62000000' /><cell cpus='16-19' memory='62000000' /><cell cpus='20-23' memory='62000000' /><cell cpus='24-27' memory='62000000' /><cell cpus='28-31' memory='62000000' /></numa></cpu> <cputune><vcpupin vcpu='0' cpuset='0' /><vcpupin vcpu='1' cpuset='2' /><vcpupin vcpu='2' cpuset='4' /><vcpupin vcpu='3' cpuset='6' /><vcpupin vcpu='4' cpuset='8' /><vcpupin vcpu='5' cpuset='10' /><vcpupin vcpu='6' cpuset='12' /><vcpupin vcpu='7' cpuset='14' /><vcpupin vcpu='8' cpuset='16' /><vcpupin vcpu='9' cpuset='18' /><vcpupin vcpu='10' cpuset='20' /><vcpupin vcpu='11' cpuset='22' /><vcpupin vcpu='12' cpuset='24' /><vcpupin vcpu='13' cpuset='26' /><vcpupin vcpu='14' cpuset='28' /><vcpupin vcpu='15' cpuset='30' /><vcpupin vcpu='16' cpuset='1' /><vcpupin vcpu='17' cpuset='3' /><vcpupin vcpu='18' cpuset='5' /><vcpupin vcpu='19' cpuset='7' /><vcpupin vcpu='20' cpuset='9' /><vcpupin vcpu='21' cpuset='11' /><vcpupin vcpu='22' cpuset='13' /><vcpupin vcpu='23' cpuset='15' /><vcpupin vcpu='24' cpuset='17' /><vcpupin vcpu='25' cpuset='19' /><vcpupin vcpu='26' cpuset='21' /><vcpupin vcpu='27' cpuset='23' /><vcpupin vcpu='28' cpuset='25' /><vcpupin vcpu='29' cpuset='27' /><vcpupin vcpu='30' cpuset='29' /><vcpupin vcpu='31' cpuset='31' /></cputune> <numatune><memory mode='preferred' nodeset='0'/></numatune>) <devices><serial type='pty'><target port='0'/></serial><console type='pty'><target type='serial' port='0'/></console><channel type='pty'><target type='virtio' name='org.qemu.guest_agent.0'/></channel></devices> <devices><hostdev mode='subsystem' type='pci' managed='yes'><source><address domain='0x0' bus='0x11' slot='0x0' function='0x1'/></source></hostdev></devices> <devices><controller type='pci' index='1' model='pci-bridge'/><controller type='pci' index='2' model='pci-bridge'/><controller type='pci' index='3' model='pci-bridge'/><controller type='pci' index='4' model='pci-bridge'/><controller type='pci' index='5' model='pci-bridge'/></devices> <metadata> <system_datastore><![CDATA[/opt/opennebula/var/datastores/108/55782]]> </system_datastore> </metadata> </domain> If I run e.g., spec2017 on the virtual, I can see: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1350 root 20 0 843136 830068 2524 R 78.1 0.2 513:16.16 bwaves_r_base.m 2456 root 20 0 804608 791264 2524 R 76.6 0.2 491:39.92 bwaves_r_base.m 4631 root 20 0 843136 829892 2344 R 75.8 0.2 450:16.04 bwaves_r_base.m 6441 root 20 0 802580 790212 2532 R 75.0 0.2 120:37.54 bwaves_r_base.m 7991 root 20 0 784676 772092 2576 R 75.0 0.2 387:15.39 bwaves_r_base.m 8142 root 20 0 843136 830044 2496 R 75.0 0.2 384:39.02 bwaves_r_base.m 8234 root 20 0 843136 830064 2524 R 75.0 0.2 99:04.48 bwaves_r_base.m 8578 root 20 0 749240 736604 2468 R 73.4 0.2 375:45.66 bwaves_r_base.m 9974 root 20 0 784676 771984 2468 R 73.4 0.2 348:01.36 bwaves_r_base.m 10396 root 20 0 802580 790264 2576 R 73.4 0.2 340:08.40 bwaves_r_base.m 12932 root 20 0 843136 830024 2480 R 73.4 0.2 288:39.76 bwaves_r_base.m 13113 root 20 0 784676 771864 2348 R 71.9 0.2 284:47.34 bwaves_r_base.m 13518 root 20 0 784676 762816 2540 R 71.9 0.2 276:31.58 bwaves_r_base.m 14443 root 20 0 784676 771984 2468 R 71.9 0.2 260:01.82 bwaves_r_base.m 12791 root 20 0 784676 772060 2544 R 70.3 0.2 291:43.96 bwaves_r_base.m 10544 root 20 0 843136 830068 2520 R 68.8 0.2 336:47.43 bwaves_r_base.m 15464 root 20 0 784676 762880 2608 R 60.9 0.2 239:19.14 bwaves_r_base.m 15487 root 20 0 784676 772048 2532 R 60.2 0.2 238:37.07 bwaves_r_base.m 16824 root 20 0 784676 772120 2604 R 55.5 0.2 212:10.92 bwaves_r_base.m 17255 root 20 0 843136 830012 2468 R 54.7 0.2 203:22.89 bwaves_r_base.m 17962 root 20 0 784676 772004 2488 R 54.7 0.2 188:26.07 bwaves_r_base.m 17505 root 20 0 843136 830068 2520 R 53.1 0.2 198:04.25 bwaves_r_base.m 27767 root 20 0 784676 771860 2344 R 52.3 0.2 592:25.95 bwaves_r_base.m 24458 root 20 0 843136 829888 2344 R 50.8 0.2 658:23.70 bwaves_r_base.m 30746 root 20 0 747376 735160 2604 R 43.0 0.2 556:47.67 bwaves_r_base.m The CPU TIME should be roughly the same but huge differences are obvious. This is what I see on the hypervizor: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 18201 oneadmin 20 0 474.0g 473.3g 1732 S 2459 94.0 33332:54 kvm 369 root 20 0 0 0 0 R 100.0 0.0 768:12.85 kswapd1 368 root 20 0 0 0 0 R 94.1 0.0 869:05.61 kswapd0 i.e., kswapd is eating whole CPU. Swap is turned off. [root@hde10 ~]# free total used free shared buff/cache available Mem: 528151432 503432580 1214048 34740 23504804 21907800 Swap: 0 0 0 Hypervisor is [root@hde10 ~]# cat /etc/redhat-release CentOS Linux release 7.5.1804 (Core) qemu-kvm-1.5.3-156.el7_5.5.x86_64 Virtual is Debian 9. Moreover, I'm using this type of disks for virtuals: <disk type='file' device='disk'> <source file='/opt/opennebula/var/datastores/108/55782/disk.3'/> <target dev='vde'/> <driver name='qemu' type='raw' cache='unsafe'/> </disk> If I keep cache='unsafe' and if I run iozone test on really big files (e.g., 8x 100GB), I can see huge cache pressure on the hypervizor - all 8 kswapd are running on 100 % percent and slowing things down. The disk under datastore is NVME SSD Intel 4500. If I set cache='none', kswaps are on idle, disk writes are pretty fast, however, with 8-NUMA configuration, writes slow down to less than 10MB/s as soon as the size of written data is roughly the same as memory size in the virtual node. iozone has 100 % CPU usage thereafter and it seems that it is traversing page lists. If I do the same with 1-NUMA configuration, everything is ok except performance penalty about 25 %. -- Lukáš Hejtmánek Linux Administrator only because Full Time Multitasking Ninja is not an official job title