I/O priorities

From OpenVZ Linux Containers Wiki
(Redirected from Ioprio)
Jump to: navigation, search

The I/O priorities feature is implemented in OpenVZ since kernel 2.6.18-028stab021, vzctl 3.0.16. This feature allows to assign I/O priority to any container. Priority range is 0-7. The more priority a container has, the more time for using block devices this container will obtain. This feature is based on CFQ I/O scheduler, so this scheduler should be used for block device in question. Default I/O priority is 4.

[edit] Examples

Set the lowest priority:

vzctl set 101 --ioprio 0 --save

Set the highest priority:

vzctl set 101 --ioprio 7 --save

[edit] Details

The higher the value you use, the more I/O time your container will receive.

The mapping from priority to time is the following: if 0 prio corresponds to time slice t, than 8 prio corresponds to time slice 2 * t. Default time slice value is HZ/2. The main criteria for fairness at the moment is that if you set I/O prio of CT 1 to p1 and I/O prio of CT 2 to p2, and p1 > p2 then CT 1 should do more I/O than CT 2. In simple form the priorities are relative with the higher priority getting more I/O time.

[edit] See also

Personal tools
Namespaces

Variants
Actions
Navigation
Other sites
Toolbox