Re: QEMU cpu socket allocation

[Peter Zay]

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 Media Services
Direct +91 44 66674575   |  Mobile +91 9043011101   |  IP 564575 rajesh.a@tatacommunications.com
www.tatacommunications.com
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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
Direct +91 44 66674575   |  Mobile +91 9043011101   |  IP 564575 rajesh.a@tatacommunications.com
www.tatacommunications.com
	@tata_comm

 

 

 

--

Peter

--

Peter