3:12 a.m.
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
Thanks in advance,
Martin
6:43 a.m.
On Mon, Nov 14, 2022 at 11:12 AM <martin.decker(a)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
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11:16 a.m.
There is a script in the RHV for HANA Guide:
https://access.redhat.com/sites/default/files/attachments/deploying_sap_h...
(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(a)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
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11:53 a.m.
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.
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'/>, but have not specified
two threads for each vCPU in the pinning field. 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?
3:54 a.m.
On Tue, Nov 15, 2022 at 05:53:13PM -0000, martin.decker(a)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?
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participants (4)
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Klaas Demter -
Liran Rotenberg -
martin.decker＠ora-solutions.net -
Tomáš Golembiovský