[PVE-User] linux idle cpu overhead in kvm - old issue, but still there in 2020...
atilav at lightspeed.ca
Tue Jul 14 18:05:43 CEST 2020
Wow, I just tried this at my servers (very old Dell PowerEdge 2950);
The results are impressive!
On 2020-07-13 3:15 a.m., Roland wrote:
> i have found that there is an old bug still around in linux, which is
> causing quite an amount of unnecessary cpu consumption in kvm/proxmox,
> and thus, wasting precious power.
> i run some proxmox installations on older systems and on those, it's
> quite significant difference.
> on the slowest system, a single debian 10 VM , kvm process is at 20% cpu
> (VM is 100% idle) when this issue is present.
> if i change VMs machine type from i440fx(default) to q35 the problem
> goes away.
> the same applies when running "powertop --auto-tune" inside the guest
> (with i440fx type - enable autosuspend for usb-controller + tablet
> on some L5630 machine, in proxmox summary i see "CPU usage" drop from
> 10% to <1%.
> i guess this information could make a difference for people who run a
> large amount of virtual machines or use older systems/cpu's.
> on most recent cpu's, i think the difference is not that big.
> anyway, i really wonder how linux bugs have such great survival
> more references:
> pve-user mailing list
> pve-user at lists.proxmox.com
More information about the pve-user