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: Alexei Potashnik <ale...@purestorage.com> --- Documentation/core-api/workqueue.rst | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst index ffdec94..3943b5b 100644 --- a/Documentation/core-api/workqueue.rst +++ b/Documentation/core-api/workqueue.rst @@ -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 =========================== -- 1.9.1
