Hello Dmitriy Rabotyagov and Sean Mooney, very thank you for your sharing. Nguyen Huu Khoi On Thu, Mar 23, 2023 at 8:50 PM Nguyễn Hữu Khôi <nguyenhuukhoinw at gmail.com> wrote: > Could you help me to explain how host cpu handle with cpu ratio? > > On Thu, Mar 23, 2023, 7:10 PM Sean Mooney <smooney at redhat.com> wrote: > >> 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 >> >> -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.openstack.org/pipermail/openstack-discuss/attachments/20230323/6dd98c7c/attachment.htm>