Re: QEMU cpu socket allocation

[Peter Zay <peterzay1@gmail.com>]

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Hi Rajesh,

>So, is it a bug that Virt Manager uses more Sockets by default, when i
choose “Copy host CPU Configuration” ?

Bug, or feature.

With a win10 client in a VM, Windows PC Health Check will complain that you
do not have enough CPUs to upgrade to win11 if you have
(Sockets,Cores,Threads) = (16,1,1).

If you have (Sockets,Cores,Threads) = (1,16,1), Windows will allow the
upgrade.

Looks like a bug.


On Wed, May 18, 2022 at 2:24 AM Rajesh A <rajesh.a@tatacommunications.com>
wrote:

> Hi Peter
>
>
>
> Thanks. Yes, I believe (Sockets,Cores,Threads) = (1,16,1) should be the
> best performance, as the VM does not need to access the memory of another
> NUMA node.
>
>
>
> So, is it a bug that Virt Manager uses more Sockets by default, when i
> choose “Copy host CPU Configuration” ?
>
>
>
> regards,
>
>
>
> *Rajesh A*
> Engineering Media Movement
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> *From:* Peter Zay <peterzay1@gmail.com>
> *Sent:* 18 May 2022 01:33 AM
> *To:* Rajesh A <rajesh.a@tatacommunications.com>
> *Cc:* qemu-discuss@nongnu.org; qemu-devel@nongnu.org; Ramya R (GIMEC) <
> ramya.r@tatacommunications.com>; V G ASHWINI . <
> Ashwini.VG@contractor.tatacommunications.com>
> *Subject:* Re: QEMU cpu socket allocation
>
>
>
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> Hi Rajesh,
>
>
>
> Would the more intuitive CPU setting of (Sockets,Cores,Threads) = (1,16,1)
> be ok?
>
>
>
> Thanks.
>
>
>
>
>
> On Tue, May 17, 2022 at 10:03 AM Rajesh A <rajesh.a@tatacommunications.com>
> wrote:
>
> Hi QEMU dev
>
>
>
> Virt Manager is able to configure a QEMU VM with more CPU sockets than the
> physical host has.
>
> For example, in the below VM, when I request 16 vCPU cores,  by default it
> takes as 16 Sockets with 1 core each. The host itself has only 2 Sockets.
>
>    1. How does QEMU allow this and how the VM works?
>    2. What is the recommended configuration of Sockets/Cores/Threads for
>    best VM performance of a 16 core VM running on a 2 sockets host ?
>
>
>
>
>
> regards,
>
>
>
> *Rajesh A*
> Engineering Media Movement
> Media Services
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> --
>
> Peter
>


-- 
Peter

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