[ovirt-users] Re: Unable to add more than 16 vCPUs to running VM

2023-06-05 Thread Gilboa Davara 
On Mon, Jun 5, 2023, 21:52 David White  wrote:

> These are Dell R630s with 2 physical CPUs.
>
> Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz
> CPU Cores per Socket:
> 8
>
> Ooooh, so even though there are 32 logical cores, the physical CPUs are
> quad core.
>
> Is there a downside to enabling "Count Threads As Cores" in the cluster
> configuration?
> Why would that not be enabled by default?
>

Hello,

SMT threads are not identical to physical cores, as two threads essentially
share the same core processing pipeline and cache, increasing the
utilization of the physical core resources.

In reality the performance will vary wildly between 1.0 to 1.5+ of that of
a single physical core.
In short,  if you really need more than 16 active vCPUs, you may get lower
performance depending on your exact workload.

Gilboa



> Sent with Proton Mail  secure email.
>
> --- Original Message ---
> On Monday, June 5th, 2023 at 2:22 PM, Gilboa Davara 
> wrote:
>
> Hello,
>
> Hardware?
> As far as I remember you cannot assign more vCPU than the number of
> physical cores you have, unless you enable "Count Threads As Cores" in
> the cluster configuration, and even than, the number of vCPUs is limited to
> the number of SMT threads you have.
>
> - Gilboa
>
> On Sun, Jun 4, 2023 at 6:17 PM David White via Users 
> wrote:
>
>> *I have a fully patched / up-to-date engine:*
>> Software Version:4.5.4-1.el8
>>
>> *And a fully patched, up-to-date host.*
>> [root@cha3-storage dwhite]# yum info ovirt-host
>> Last metadata expiration check: 1:33:40 ago on Sun 04 Jun 2023 09:28:39
>> AM EDT.
>> Installed Packages
>> Name : ovirt-host
>> Version : 4.5.0
>> Release : 3.el8
>> Architecture : x86_64
>> Size : 11 k
>> Source : ovirt-host-4.5.0-3.el8.src.rpm
>> Repository : @System
>> From repo : centos-ovirt45
>>
>> The host has 32GB of RAM, and there's only 1 VM on this host.
>> When I try to add more CPUs to the VM from the manager UI, I get the
>> following error:
>>
>>- *The requested number of vCPUs is not available on the host the VM
>>is running on*
>>
>> What's going on here, and why can I not add more vCPUs to this VM?
>>
>> Sent with Proton Mail  secure email.
>> ___
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>>
>
>
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[ovirt-users] Re: Unable to add more than 16 vCPUs to running VM

2023-06-05 Thread David White via Users 
These are Dell R630s with 2 physical CPUs.

Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz
CPU Cores per Socket:
8
Ooooh, so even though there are 32 logical cores, the physical CPUs are quad 
core.

Is there a downside to enabling "Count Threads As Cores" in the cluster 
configuration?
Why would that not be enabled by default?


Sent with Proton Mail secure email.

--- Original Message ---
On Monday, June 5th, 2023 at 2:22 PM, Gilboa Davara  wrote:


> Hello,
> 

> Hardware?
> As far as I remember you cannot assign more vCPU than the number of physical 
> cores you have, unless you enable "Count Threads As Cores" in the cluster 
> configuration, and even than, the number of vCPUs is limited to the number of 
> SMT threads you have.
> 

> 

> - Gilboa
> 

> 

> On Sun, Jun 4, 2023 at 6:17 PM David White via Users  wrote:
> 

> > I have a fully patched / up-to-date engine:
> > Software Version:4.5.4-1.el8
> > 

> > 

> > And a fully patched, up-to-date host.
> > [root@cha3-storage dwhite]# yum info ovirt-hostLast metadata expiration 
> > check: 1:33:40 ago on Sun 04 Jun 2023 09:28:39 AM EDT.
> > Installed Packages
> > Name : ovirt-host
> > Version : 4.5.0
> > Release : 3.el8
> > Architecture : x86_64
> > Size : 11 k
> > Source : ovirt-host-4.5.0-3.el8.src.rpm
> > Repository : @System
> > From repo : centos-ovirt45
> > 

> > 

> > 

> > The host has 32GB of RAM, and there's only 1 VM on this host.
> > When I try to add more CPUs to the VM from the manager UI, I get the 
> > following error:
> > 

> > -   The requested number of vCPUs is not available on the host the VM is 
> > running on
> > 

> > What's going on here, and why can I not add more vCPUs to this VM?
> > 

> > 

> > 

> > Sent with Proton Mail secure email.
> > ___
> > 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/5ANM4TY6DOYG7WNVOCBWUZR6OUKV5BYQ/

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[ovirt-users] Re: Unable to add more than 16 vCPUs to running VM

2023-06-05 Thread Gilboa Davara 
Hello,

Hardware?
As far as I remember you cannot assign more vCPU than the number of
physical cores you have, unless you enable "Count Threads As Cores" in the
cluster configuration, and even than, the number of vCPUs is limited to the
number of SMT threads you have.

- Gilboa

On Sun, Jun 4, 2023 at 6:17 PM David White via Users 
wrote:

> *I have a fully patched / up-to-date engine:*
> Software Version:4.5.4-1.el8
>
> *And a fully patched, up-to-date host.*
> [root@cha3-storage dwhite]# yum info ovirt-host
> Last metadata expiration check: 1:33:40 ago on Sun 04 Jun 2023 09:28:39 AM
> EDT.
> Installed Packages
> Name : ovirt-host
> Version  : 4.5.0
> Release  : 3.el8
> Architecture : x86_64
> Size : 11 k
> Source   : ovirt-host-4.5.0-3.el8.src.rpm
> Repository   : @System
> From repo: centos-ovirt45
>
> The host has 32GB of RAM, and there's only 1 VM on this host.
> When I try to add more CPUs to the VM from the manager UI, I get the
> following error:
>
>- *The requested number of vCPUs is not available on the host the VM
>is running on*
>
> What's going on here, and why can I not add more vCPUs to this VM?
>
> Sent with Proton Mail  secure email.
> ___
> 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/5ANM4TY6DOYG7WNVOCBWUZR6OUKV5BYQ/
>
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