[kata-dev] CPU constraint translation to Qemu SMP options

Whaley, Graham graham.whaley at intel.com
Wed Jun 20 16:03:33 UTC 2018


I'm pretty sure Julio(devimc) can answer better - but...

I believe we use sockets as we can hotplug those, and we cannot hotplug CPU cores (pls correct me Julio if I've got that wrong)
And there is a discussion/thread right now to clarify why asking for 8 cpus gets you 9 (I have a theory, but I'll leave that one for Julio as well ;-).

Graham

> -----Original Message-----
> From: Edupuganti, Saikrishna [mailto:saikrishna.edupuganti at intel.com]
> Sent: Wednesday, June 20, 2018 4:50 PM
> To: kata-dev at lists.katacontainers.io
> Subject: [kata-dev] CPU constraint translation to Qemu SMP options
> 
> Hi Team,
> 
> When translating the K cpu count from Docker/k8s to Qemu options, what is
> reasoning behind configuring K sockets with 1 core per socket instead of K cores
> with 1 socket? Did any performance measurements guide this decision?
> 
> When we bring up kata container with 8 cpus it brings up a VM with (8+1)
> sockets -
> 
> kubectl exec -it ubuntu-kata -- lscpu
> Architecture:          x86_64
> CPU op-mode(s):        32-bit, 64-bit
> Byte Order:            Little Endian
> CPU(s):                1
> On-line CPU(s) list:   0
> Thread(s) per core:    1
> Core(s) per socket:    1
> Socket(s):             1
> 
> kubectl exec -it ubuntu-kata-8cpu-limit -- lscpu
> Architecture:          x86_64
> CPU op-mode(s):        32-bit, 64-bit
> Byte Order:            Little Endian
> CPU(s):                9
> On-line CPU(s) list:   0-8
> Thread(s) per core:    1
> Core(s) per socket:    1
> Socket(s):             9
> 
> Thanks,
> Sai
> 
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