Difference between revisions of "I/O priorities"
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| − | The I/O priorities feature is implemented in OpenVZ since kernel <tt>2.6.18- | + | The I/O priorities feature is implemented in OpenVZ since kernel <tt>2.6.18-028stab021</tt>, <tt>vzctl 3.0.16</tt>. This feature allows to assign I/O priority to any [[container]]. Priority range is <tt>0-7</tt>. 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 <tt>4</tt>. |
== Examples == | == Examples == | ||
Revision as of 11:13, 13 December 2013
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.
Examples
Set the lowest priority:
vzctl set 101 --ioprio 0 --save
Set the highest priority:
vzctl set 101 --ioprio 7 --save
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.
