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@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@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...
https://docs.openstack.org/nova/latest/configuration/config.html#compute.cpu...
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.res...
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...
which means if you decide to manage that via placement api by using
https://docs.openstack.org/nova/latest/configuration/config.html#DEFAULT.ini... 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