On Mon, Nov 14, 2022 at 11:12 AM <martin.dec...@ora-solutions.net> wrote:
> Hello List, > > how can I achieve the best performance with vcpu pinning in KVM? > > Is it better to have 1:1 mapping between virtual and physical thread like > this: > > <vcpupin vcpu='0' cpuset='0'/> > <vcpupin vcpu='1' cpuset='1'/> > <vcpupin vcpu='2' cpuset='2'/> > <vcpupin vcpu='3' cpuset='3'/> > <vcpupin vcpu='4' cpuset='4'/> > <vcpupin vcpu='5' cpuset='5'/> > <vcpupin vcpu='6' cpuset='6'/> > <vcpupin vcpu='7' cpuset='7'/> > > Or is it better to allow each vCPU to run on any of the limited number of > physical threads? > > e.g. > <vcpupin vcpu='0' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='1' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='2' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='3' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='4' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='5' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='6' cpuset='0,1,2,3,4,5,6,7'/> > <vcpupin vcpu='7' cpuset='0,1,2,3,4,5,6,7'/> > > > The hypervisor host has 2 CPUs. Each CPU has 8 cores and each core 2 > Threads. In total this are 32 threads. > > 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: 2 > Core(s) per socket: 8 > Socket(s): 2 > NUMA node(s): 2 > Vendor ID: GenuineIntel > CPU family: 6 > Model: 85 > Model name: Intel(R) Xeon(R) Gold 6244 CPU @ 3.60GHz > Stepping: 7 > CPU MHz: 4213.731 > CPU max MHz: 4400.0000 > CPU min MHz: 1200.0000 > BogoMIPS: 7200.00 > Virtualization: VT-x > L1d cache: 32K > L1i cache: 32K > L2 cache: 1024K > L3 cache: 25344K > NUMA node0 CPU(s): 0-7,16-23 > NUMA node1 CPU(s): 8-15,24-31 > > I need to run 2 VMs on this host. One is for production and should have 24 > vCPUs and the other one is for test and should have 8 vCPUs. Test VM > workload should not impact Prod VM performance. > > Current configuration is: > > TEST: > > <vcpu placement='static' current='8'>128</vcpu> > <iothreads>1</iothreads> > <cputune> > <vcpupin vcpu='0' cpuset='0'/> > <vcpupin vcpu='1' cpuset='1'/> > <vcpupin vcpu='2' cpuset='2'/> > <vcpupin vcpu='3' cpuset='3'/> > <vcpupin vcpu='4' cpuset='4'/> > <vcpupin vcpu='5' cpuset='5'/> > <vcpupin vcpu='6' cpuset='6'/> > <vcpupin vcpu='7' cpuset='7'/> > </cputune> > > <cpu mode='host-passthrough' check='none'> > <topology sockets='16' cores='4' threads='2'/> > <numa> > <cell id='0' cpus='0-7' memory='134217728' unit='KiB'/> > </numa> > </cpu> > > PROD: > > <vcpu placement='static' current='24'>192</vcpu> > <iothreads>1</iothreads> > <cputune> > <vcpupin vcpu='0' cpuset='8'/> > <vcpupin vcpu='1' cpuset='9'/> > <vcpupin vcpu='2' cpuset='10'/> > <vcpupin vcpu='3' cpuset='11'/> > <vcpupin vcpu='4' cpuset='12'/> > <vcpupin vcpu='5' cpuset='13'/> > <vcpupin vcpu='6' cpuset='14'/> > <vcpupin vcpu='7' cpuset='15'/> > <vcpupin vcpu='8' cpuset='16'/> > <vcpupin vcpu='9' cpuset='17'/> > <vcpupin vcpu='10' cpuset='18'/> > <vcpupin vcpu='11' cpuset='19'/> > <vcpupin vcpu='12' cpuset='20'/> > <vcpupin vcpu='13' cpuset='21'/> > <vcpupin vcpu='14' cpuset='22'/> > <vcpupin vcpu='15' cpuset='23'/> > <vcpupin vcpu='16' cpuset='24'/> > <vcpupin vcpu='17' cpuset='25'/> > <vcpupin vcpu='18' cpuset='26'/> > <vcpupin vcpu='19' cpuset='27'/> > <vcpupin vcpu='20' cpuset='28'/> > <vcpupin vcpu='21' cpuset='29'/> > <vcpupin vcpu='22' cpuset='30'/> > <vcpupin vcpu='23' cpuset='31'/> > </cputune> > > <cpu mode='host-passthrough' check='none'> > <topology sockets='16' cores='6' threads='2'/> > <numa> > <cell id='0' cpus='0-23' memory='889192448' unit='KiB'/> > </numa> > </cpu> > > Versions are: > ovirt-host-4.3.5 > libvirt-5.7.0-28.el7.x86_64 > Hi Martin, The recommended approach would be to pin the CPUs into specific physical CPUs. The most important part is to be under the same socket. VDSM uses physical CPU 1, unless you changed the default VDSM settings, so maybe it would be better to use the second socket. You may also wish to refer to the NUMA topology (using socket 1 that would be - NUMA node1 CPU(s): 8-15,24-31). Overall: 0#8,24_1#9,25_2#10,26 and so on. This is also with the thought that physical cpu 8 and 24 are two threads in the same core. You can check it using VDSM API or just # cat /proc/cpuinfo. Note, that physical CPUs you use with this method are in a shared pool and can be used by other VMs. If you wish it to be exclusive to the VM, you may use the dedicated CPU feature under the VM resource allocation tab. Note, it will pin the CPUs for you. Regards, Liran. > Thanks in advance, > Martin > _______________________________________________ > Users mailing list -- users@ovirt.org > To unsubscribe send an email to users-le...@ovirt.org > Privacy Statement: https://www.ovirt.org/privacy-policy.html > oVirt Code of Conduct: > https://www.ovirt.org/community/about/community-guidelines/ > List Archives: > https://lists.ovirt.org/archives/list/users@ovirt.org/message/HCNWYSIBMUY7Q3YU25KQL2MUCK42GMJ6/ >
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