There is a script in the RHV for HANA Guide: https://access.redhat.com/sites/default/files/attachments/deploying_sap_hana... (search for "Calculate CPU Pinning") Greetings Klaas On 11/14/22 13:43, Liran Rotenberg wrote:

On Mon, Nov 14, 2022 at 11:12 AM <martin.decker@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-leave@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/HCNWYSIBMUY7Q3...

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On Tue, Nov 15, 2022 at 05:53:13PM -0000, martin.decker@ora-solutions.net wrote:

Hi Klaas,

in our case, the Hypervisor CPU looks like this:

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 NUMA node0 CPU(s): 0-7,16-23 NUMA node1 CPU(s): 8-15,24-31

The PROD VM should have 24 PINNED (due to licensing requirements) vCPUs out of the 32 threads and around 838G of the 1 TB RAM. The TEST VM should have 8 vCPUs out of the 32 threads and around 128G of 1 TB RAM.

With these PROD VM Requirements, it does not make sense to limit vCPUs to one socket / NUMA node. The TEST VM can be limited to one socket.

In this case the option here would be to actually define two vNUMA in your PROD and TEST VMs. Give your PROD VM 12+12 and your TEST VM 4+4. Then make sure to define the pinning so that vCPUs of one vNUMA align with CPUs of physical NUMA. Also sharing the CPU that VDSM is using with the TEST VM might be preferable unless you want to share some CPUs between TEST and PROD. So like this: TEST: pCPUs 0,1,16,17 map to first vNUMA pCPUs 8,9,24,25 map to second vNUMA PROD: pCPUs 2-7,18-23 map to first vNUMA pCPUS 10-15,26-31 map to second vNUMA

I guess I have made these mistakes:

- I should not use Physical CPU thread 0 but leave it for Hypervisor - I have configured the VM "2 threads per core" with <topology sockets='16' cores='6' threads='2'/>,

This does not add up. 16 sockets is bit too much. I think you meant 2 sockets.

but have not specified two threads for each vCPU in the pinning field.

I don't think this is strictly necessary. But you definitely want to make sure that the virtual threads match the physical threads. In other words you only want to mix and match pCPUs 0 and 16 (or 1 and 17, etc.) so I would say 0#0_1#16 is fine just like 0#0,16_1#0,16. Alternatively you may define only single threaded VM (topology 2:12:1) and don't care about the physical threads that much. Which of the alternatives is best would depend on your workload in the guest and how well it can benefit from the knowledge of the host topology. Hope this helps Tomas

In the oVirt "Resource Allocation" Tab in "CPU Pinning Topology", i have specified: 0#8_1#9_2#10_3#11_4#12_5#13_6#14_7#15_8#16_9#17_10#18_11#19_12#20_13#21_14#22_15#23_16#24_17#25_18#26_19#27_20#28_21#29_22#30_23#31

The Calculate CPU Pinning script from the RHV HANA Guide results in this mapping:

0#1,17 1#1,17 2#2,18 3#2,18 4#3,19 5#3,19 6#4,20 7#4,20 8#5,21 9#5,21 10#6,22 11#6,22 12#9,25 13#9,25 14#10,26 15#10,26 16#11,27 17#11,27 18#12,28 19#12,28 20#13,29 21#13,29 22#14,30 23#14,30

But with this approach, I can not separate CPUs between PROD VM and TEST VM.

Any ideas? _______________________________________________ Users mailing list -- users@ovirt.org To unsubscribe send an email to users-leave@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/PF7UCDGZPL3FJ4...