Sockets to Core Ratio

[Marty Godsey <ma...@rudio.net>]

Hello,


When Cloudstack creates a VM on my XCP cluster, it always adds more sockets than I would like to have. So, for example, if I have a compute offering that is 4 cores, It's 2 sockets, 2 cores. Why can't it be 1 socket and 4 cores? If this is something that is not being don’t by Cloudstack and XCP, I will go that route. Any one seen this?


Thank you everyone.

Re: Sockets to Core Ratio

[João Jandre Paraquetti <jo...@scclouds.com.br>]

Hello, Marty

During the VM deploy on XenServer/xcp-ng, the property 
|cores-per-socket| is retrieved directly from the hypervisor's 
templates. During the creation of the VM, ACS fetches the template from 
Xen's API, using the OS configured on the VM's template as the 
paremeter. These templates have many configurations that are the 
hypervisor's defaults, between them, there is the |cores-per-socket|. On 
my xcp-ng environment, the Windows VMs have the |cores-per-socket:2| value.

To check this, you may list all the templates using the |xe 
template-list| command:

|[15:17 xcp-ng-wfokjhs ~]# xe template-list ... uuid ( RO) : 
7774689b-4ca1-4dea-8545-dddd6b64c17f name-label ( RW): Windows 10 
(64-bit) name-description ( RW): Clones of this template will 
automatically provision their storage when first booted and then 
reconfigure themselves with the optimal settings for Windows 10 
(64-bit). ... |

Then, you may list the template parameters using the |xe 
template-param-list uuid=<template_uuid>|, then, in the platform 
attribute, you will see a map of the parameters used for the template, 
including the |cores-per-socket|, if it is set:

|[15:17 xcp-ng-wfokjhs ~]# xe template-param-list 
uuid=7774689b-4ca1-4dea-8545-dddd6b64c17f uuid ( RO) : 
7774689b-4ca1-4dea-8545-dddd6b64c17f name-label ( RW): Windows 10 
(64-bit) ... platform (MRW): videoram: 8; hpet: true; acpi_laptop_slate: 
1; secureboot: auto; viridian_apic_assist: true; apic: true; device_id: 
0002; cores-per-socket: 2; viridian_crash_ctl: true; pae: true; vga: 
std; nx: true; viridian_time_ref_count: true; viridian_stimer: true; 
viridian: true; acpi: 1; viridian_reference_tsc: true allowed-operations 
(SRO): changing_NVRAM; changing_dynamic_range; changing_shadow_memory; 
changing_static_range; provision; export; clone; copy ... |

There are two ways to overcome this, you may change the Xen template 
configurations directly, using the |xe template-param-remove 
uuid=<template_uuid> param-name=platform param-key=cores-per-socket| for 
example, to remove the parameter; I believe that you can use 
|template-param-set| to change the param's value as well, but I have not 
tested it. The second way is to stop the VM and edit the |platform| 
setting, changing the value as you wish and then starting the VM.

Beware that changing the CPU topology may affect the guest OS and should 
be done with caution.

Best regards,
João Jandre

On 12/4/25 10:27, Marty Godsey wrote:
> 100% Nux.
>
> I tried adding this as an additional field to the offering, but it was not honored.
>
> Plus depending on the OS, the other sockets may not even be seen. As an example, Windows 10/11, I know this is a non-relistic example, but it gets the point across. If I have a VM with 16 vCPUs assigned and it spins up with 1 socket with16 cores, I am fine. But if it spins up the VM with 4 sockets, each with 4 cores, two of those sockets will not be seen by the OS because it only supports 2 sockets.
>
>
> From: Nux<nu...@li.nux.ro>
> Date: Thursday, December 4, 2025 at 4:18 AM
> To:users@cloudstack.apache.org  <us...@cloudstack.apache.org>
> Cc: Wei ZHOU<us...@gmail.com>
> Subject: Re: Sockets to Core Ratio
>
> WARNING: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
>
> It'd be nice to be able to set this in the compute offering as it can
> impact licensing of various proprietary software.
> I know, it's stupid, but people pay more if they have more sockets, as
> opposed to cores.
> There could be other considerations as well.
>
> Regards
>
> On 2025-12-04 07:23, Wei ZHOU wrote:
>> Hi,
>>
>> You can stop the vm, add a vm setting cpu.corespersocket=4, and then
>> start
>> the vm.
>>
>>
>> Kind regards,
>> Wei
>>
>>
>> On Thu, Dec 4, 2025 at 7:56 AM Marty Godsey<ma...@rudio.net>  wrote:
>>
>>> Hello,
>>>
>>>
>>> When Cloudstack creates a VM on my XCP cluster, it always adds more
>>> sockets than I would like to have. So, for example, if I have a
>>> compute
>>> offering that is 4 cores, It's 2 sockets, 2 cores. Why can't it be 1
>>> socket
>>> and 4 cores? If this is something that is not being don’t by
>>> Cloudstack and
>>> XCP, I will go that route. Any one seen this?
>>>
>>>
>>> Thank you everyone.
>>>

Re: Sockets to Core Ratio

[Marty Godsey <ma...@rudio.net>]

100% Nux.

I tried adding this as an additional field to the offering, but it was not honored.

Plus depending on the OS, the other sockets may not even be seen. As an example, Windows 10/11, I know this is a non-relistic example, but it gets the point across. If I have a VM with 16 vCPUs assigned and it spins up with 1 socket with16 cores, I am fine. But if it spins up the VM with 4 sockets, each with 4 cores, two of those sockets will not be seen by the OS because it only supports 2 sockets.


From: Nux <nu...@li.nux.ro>
Date: Thursday, December 4, 2025 at 4:18 AM
To: users@cloudstack.apache.org <us...@cloudstack.apache.org>
Cc: Wei ZHOU <us...@gmail.com>
Subject: Re: Sockets to Core Ratio

WARNING: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.


It'd be nice to be able to set this in the compute offering as it can
impact licensing of various proprietary software.
I know, it's stupid, but people pay more if they have more sockets, as
opposed to cores.
There could be other considerations as well.

Regards

On 2025-12-04 07:23, Wei ZHOU wrote:
> Hi,
>
> You can stop the vm, add a vm setting cpu.corespersocket=4, and then
> start
> the vm.
>
>
> Kind regards,
> Wei
>
>
> On Thu, Dec 4, 2025 at 7:56 AM Marty Godsey <ma...@rudio.net> wrote:
>
>>
>> Hello,
>>
>>
>> When Cloudstack creates a VM on my XCP cluster, it always adds more
>> sockets than I would like to have. So, for example, if I have a
>> compute
>> offering that is 4 cores, It's 2 sockets, 2 cores. Why can't it be 1
>> socket
>> and 4 cores? If this is something that is not being don’t by
>> Cloudstack and
>> XCP, I will go that route. Any one seen this?
>>
>>
>> Thank you everyone.
>>

Re: Sockets to Core Ratio

[Nux <nu...@li.nux.ro>]

It'd be nice to be able to set this in the compute offering as it can 
impact licensing of various proprietary software.
I know, it's stupid, but people pay more if they have more sockets, as 
opposed to cores.
There could be other considerations as well.

Regards

On 2025-12-04 07:23, Wei ZHOU wrote:
> Hi,
> 
> You can stop the vm, add a vm setting cpu.corespersocket=4, and then 
> start
> the vm.
> 
> 
> Kind regards,
> Wei
> 
> 
> On Thu, Dec 4, 2025 at 7:56 AM Marty Godsey <ma...@rudio.net> wrote:
> 
>> 
>> Hello,
>> 
>> 
>> When Cloudstack creates a VM on my XCP cluster, it always adds more
>> sockets than I would like to have. So, for example, if I have a 
>> compute
>> offering that is 4 cores, It's 2 sockets, 2 cores. Why can't it be 1 
>> socket
>> and 4 cores? If this is something that is not being don’t by 
>> Cloudstack and
>> XCP, I will go that route. Any one seen this?
>> 
>> 
>> Thank you everyone.
>> 

Re: Sockets to Core Ratio

[Wei ZHOU <us...@gmail.com>]

Hi,

You can stop the vm, add a vm setting cpu.corespersocket=4, and then start
the vm.


Kind regards,
Wei


On Thu, Dec 4, 2025 at 7:56 AM Marty Godsey <ma...@rudio.net> wrote:

>
> Hello,
>
>
> When Cloudstack creates a VM on my XCP cluster, it always adds more
> sockets than I would like to have. So, for example, if I have a compute
> offering that is 4 cores, It's 2 sockets, 2 cores. Why can't it be 1 socket
> and 4 cores? If this is something that is not being don’t by Cloudstack and
> XCP, I will go that route. Any one seen this?
>
>
> Thank you everyone.
>