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Commit 0e0cafcd authored by Alexei Potashnik's avatar Alexei Potashnik Committed by Tejun Heo
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workqueue: doc change for ST behavior on NUMA systems 



NUMA rework of workqueue made the combination of max_active of 1 and
WQ_UNBOUND insufficient to guarantee ST behavior system wide.

alloc_ordered_queue should now be used instead.

Signed-off-by: default avatarAlexei Potashnik <alexei@purestorage.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent bef85bd7

Documentation/core-api/workqueue.rst

+7 −3
Original line number Diff line number Diff line
@@ -243,11 +243,15 @@ throttling the number of active work items, specifying '0' is 
recommended.



Some users depend on the strict execution ordering of ST wq.  The

combination of ``@max_active`` of 1 and ``WQ_UNBOUND`` is used to

achieve this behavior.  Work items on such wq are always queued to the

unbound worker-pools and only one work item can be active at any given

combination of ``@max_active`` of 1 and ``WQ_UNBOUND`` used to

achieve this behavior.  Work items on such wq were always queued to the

unbound worker-pools and only one work item could be active at any given

time thus achieving the same ordering property as ST wq.



In the current implementation the above configuration only guarantees

ST behavior within a given NUMA node. Instead alloc_ordered_queue should

be used to achieve system wide ST behavior.





Example Execution Scenarios

===========================