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Ok. I will try to understand it. I will let you know when I get it.
Many thanks for your help. :)

On Thu, Mar 23, 2023, 8:14 PM Dmitriy Rabotyagov <noonedeadpunk at gmail.com>
wrote:

> Just to double check with you, given that you have
> cpu_overcommit_ratio>1, 2 sockets and HT enabled, and each CPU has 32
> physical cores, then it should be defined like:
>
> [compute]
> cpu_shared_set="2-32,34-64,66-96,98-128"?
>
> > in general you shoudl reserve the first core on each cpu socket for the
> host os.
> > if you use hyperthreading then both hyperthread of the first cpu core on
> each socket shoudl be omitted
> > form the cpu_shared_set and cpu_dedicated_set
>
> чт, 23 мар. 2023 г. в 13:12, Sean Mooney <smooney at redhat.com>:
> >
> > generally you should not
> > you can use it but the preferd way to do this is use
> > cpu_shared_set and cpu_dedicated_set (in old releases you would have
> used vcpu_pin_set)
> >
> https://docs.openstack.org/nova/latest/configuration/config.html#compute.cpu_shared_set
> >
> https://docs.openstack.org/nova/latest/configuration/config.html#compute.cpu_dedicated_set
> >
> > if you dont need cpu pinning just use cpu_share_set to spcify the cores
> that can be sued for floatign vms
> > when you use cpu_shared_set and cpu_dedicated_set any cpu not specified
> are reseved for host use.
> >
> > https://that.guru/blog/cpu-resources/ and
> https://that.guru/blog/cpu-resources-redux/
> >
> > have some useful info but that mostly looking at it form a cpu pinning
> angel althoguh the secon one covers cpu_shared_set,
> >
> > the issue with usein
> >
> https://docs.openstack.org/nova/latest/configuration/config.html#DEFAULT.reserved_host_cpus
> >
> > is that you have to multiple the number of cores that are resverved by
> the
> >
> https://docs.openstack.org/nova/latest/configuration/config.html#DEFAULT.cpu_allocation_ratio
> >
> > which means if you decide to manage that via placement api by using
> >
> https://docs.openstack.org/nova/latest/configuration/config.html#DEFAULT.initial_cpu_allocation_ratio
> instead
> > then you need to update your nova.conf to modify the reservationfi you
> change the allocation ratio.
> >
> > if instead you use cpu_shared_set and cpu_dedicated_set
> > you are specifying exactly which cpus nova can use and the allocation
> ration nolonger needs to be conisderd.
> >
> > in general you shoudl reserve the first core on each cpu socket for the
> host os.
> > if you use hyperthreading then both hyperthread of the first cpu core on
> each socket shoudl be omitted
> > form the cpu_shared_set and cpu_dedicated_set
> >
> >
> >
> > On Thu, 2023-03-23 at 14:44 +0700, Nguyễn Hữu Khôi wrote:
> > > Hello guys.
> > > I am trying google for nova host cpu reserve to prevent host overload
> but I
> > > cannot find any resource about it. Could you give me some information?
> > > Thanks.
> > > Nguyen Huu Khoi
> >
> >
>
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