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Merge pull request #7837 from rldleblanc/wpq-documentation

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doc: osd-config Add Configuration Options for op queue.
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Sage Weil 2016-03-01 09:27:21 -05:00
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doc/rados/configuration/osd-config-ref.rst
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@ -331,6 +331,42 @@ recovery operations to ensure optimal performance during recovery.
:Default: ``2``
``osd op queue``
:Description: This sets the type of queue to be used for prioritizing ops
in the OSDs. Both queues feature a strict sub-queue which is
dequeued before the normal queue. The normal queue is different
between implementations. The original PrioritizedQueue (``prio``) uses a
token bucket system which when there are sufficient tokens will
dequeue high priority queues first. If there are not enough
tokens available, queues are dequeued low priority to high priority.
The new WeightedPriorityQueue (``wpq``) dequeues all priorities in
relation to their priorities to prevent starvation of any queue.
WPQ should help in cases where a few OSDs are more overloaded
than others. Requires a restart.
:Type: String
:Valid Choices: prio, wpq
:Default: ``prio``
``osd op queue cut off``
:Description: This selects which priority ops will be sent to the strict
queue verses the normal queue. The ``low`` setting sends all
replication ops and higher to the strict queue, while the ``high``
option sends only replication acknowledgement ops and higher to
the strict queue. Setting this to ``high`` should help when a few
OSDs in the cluster are very busy especially when combined with
``wpq`` in the ``osd op queue`` setting. OSDs that are very busy
handling replication traffic could starve primary client traffic
on these OSDs without these settings. Requires a restart.
:Type: String
:Valid Choices: low, high
:Default: ``low``
``osd client op priority``
:Description: The priority set for client operations. It is relative to