proxmox-mirrors/pve-docs
1
0
Fork 0
mirror of https://git.proxmox.com/git/pve-docs synced 2025-05-09 16:56:23 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

qm: resource limits: reword cpulimit section

Browse Source 
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
This commit is contained in:
Thomas Lamprecht 2024-02-20 13:28:46 +01:00
parent b3848f246c
commit 0186a4671a
1 changed files with 12 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
qm.adoc
View File

@ -347,16 +347,19 @@ fully it would theoretically use `400%`. In reality the usage may be even a bit
higher as QEMU can have additional threads for VM peripherals besides the vCPU
core ones.
This setting can be useful if a VM should have multiple vCPUs, as it runs a few
processes in parallel, but the VM as a whole should not be able to run all
vCPUs at 100% at the same time.
This setting can be useful when a VM should have multiple vCPUs because it is
running some processes in parallel, but the VM as a whole should not be able to
run all vCPUs at 100% at the same time.
Using a specific example: lets say we have a VM which would profit from having
8 vCPUs, but at no time all of those 8 cores should run at full load - as this
would make the server so overloaded that other VMs and CTs would get too less
CPU. So, we set the *cpulimit* limit to `4.0` (=400%). If we now fully utilize
all 8 vCPUs, they will receive maximum 50% CPU time of the physical cores. But
with only 4 vCPUs fully utilized, they could still get up to 100% CPU time.
For example, suppose you have a virtual machine that would benefit from having 8
virtual CPUs, but you don't want the VM to be able to max out all 8 cores
running at full load - because that would overload the server and leave other
virtual machines and containers with too little CPU time. To solve this, you
could set *cpulimit* to `4.0` (=400%). This means that if the VM fully utilizes
all 8 virtual CPUs by running 8 processes simultaneously, each vCPU will receive
a maximum of 50% CPU time from the physical cores. However, if the VM workload
only fully utilizes 4 virtual CPUs, it could still receive up to 100% CPU time
from a physical core, for a total of 400%.
NOTE: VMs can, depending on their configuration, use additional threads, such
as for networking or IO operations but also live migration. Thus a VM can show