correajl opened a new issue, #6744:
URL: https://github.com/apache/cloudstack/issues/6744
##### ISSUE TYPE
<!-- Pick one below and delete the rest -->
* Improvement Request
##### COMPONENT NAME
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Cloudstack management and cloudstack agent.
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##### CLOUDSTACK VERSION
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4.17.0.1
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##### CONFIGURATION
2 management servers, 2 databases, advanced network, everything working
fine.
##### OS / ENVIRONMENT
Ubuntu Server 22.04 LTS, KVM, libvirt 8.0.0-1ubuntu7.1, cgroup2.
##### SUMMARY
The value of "CPU (in MHz)" used in some compute offering definitions is
mapped to 'shares' element in 'cputune' section of domain definition file
(xml). According to [libvirt documentation](libvirt.org/formatdomain.html) the
value should be in range [2, 262144]. But, for operating systems using cgroup
v2 the maximum value is 10000. I know that Ubuntu 22.04 I'm using here is not
supported yet. But this will be an issue as other OSs adopt cgroup v2 too. So,
I think this parameter deserves attention. If the value of (N. CPU) * CPU (in
MHz) is greater than 10000 I get "**Value specified in CPUWeight is out of
range**" in hypervisor.
As a workaround I configured service offering with 1 Mhz. This implies that
VMs with more CPUs have much more chance to get the CPU than VMs with lower
number of CPUs, because besides having more CPUs, they have more chance to get
the host' CPUs.
VM1 10 CPU * 1 MHz -> shares = 10
VM2 80 CPU * 1 MHz -> shares = 80
If we look at 1st CPU of VM2, it will have 8 times more chance to get the
host's CPU than 1st CPU of VM1.
Shouldn't all virtual CPUs have the same chance of using one host CPU?
##### STEPS TO REPRODUCE
Using Ubuntu 22.04 or other OS that uses cgroup v2, create a compute
offering with a CPU (in MHz) value of 1000. Try to launch an instance with more
than 10 CPUs. It will be generated a configuration file for the new instance
with shares > 10000 inside cputune section. Hypervisor can't launch the
instance with _Value specified in CPUWeight is out of range_ error.
##### EXPECTED RESULTS
Create a way for all virtual CPUs to have an equal chance of using a host
CPU.
Check cgroup version and try to not generate values bigger than 10000.
##### ACTUAL RESULTS
Working in this way when the CPU (in MHz) is mapped to the 'shares' element,
instances with fewer CPUs are always penalized. Sometimes hosts can't launch
instances.
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