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authorLinus Torvalds <torvalds@linux-foundation.org>2010-10-22 17:13:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-22 17:13:10 -0700
commit91b745016c12d440386c40fb76ab69c8e08cbc06 (patch)
tree881a26a43b3ee924c0979a54b38c7a87d79d7f1a /Documentation
parent04cc69768e7d1f40d98b79d23d203674553b4da2 (diff)
parentdaaae6b010ac0f60c9c35e481589966f9f1fcc22 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: workqueue: remove in_workqueue_context() workqueue: Clarify that schedule_on_each_cpu is synchronous memory_hotplug: drop spurious calls to flush_scheduled_work() shpchp: update workqueue usage pciehp: update workqueue usage isdn/eicon: don't call flush_scheduled_work() from diva_os_remove_soft_isr() workqueue: add and use WQ_MEM_RECLAIM flag workqueue: fix HIGHPRI handling in keep_working() workqueue: add queue_work and activate_work trace points workqueue: prepare for more tracepoints workqueue: implement flush[_delayed]_work_sync() workqueue: factor out start_flush_work() workqueue: cleanup flush/cancel functions workqueue: implement alloc_ordered_workqueue() Fix up trivial conflict in fs/gfs2/main.c as per Tejun
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/workqueue.txt29
1 files changed, 15 insertions, 14 deletions
diff --git a/Documentation/workqueue.txt b/Documentation/workqueue.txt
index e4498a2872c..996a27d9b8d 100644
--- a/Documentation/workqueue.txt
+++ b/Documentation/workqueue.txt
@@ -196,11 +196,11 @@ resources, scheduled and executed.
suspend operations. Work items on the wq are drained and no
new work item starts execution until thawed.
- WQ_RESCUER
+ WQ_MEM_RECLAIM
All wq which might be used in the memory reclaim paths _MUST_
- have this flag set. This reserves one worker exclusively for
- the execution of this wq under memory pressure.
+ have this flag set. The wq is guaranteed to have at least one
+ execution context regardless of memory pressure.
WQ_HIGHPRI
@@ -356,11 +356,11 @@ If q1 has WQ_CPU_INTENSIVE set,
6. Guidelines
-* Do not forget to use WQ_RESCUER if a wq may process work items which
- are used during memory reclaim. Each wq with WQ_RESCUER set has one
- rescuer thread reserved for it. If there is dependency among
- multiple work items used during memory reclaim, they should be
- queued to separate wq each with WQ_RESCUER.
+* Do not forget to use WQ_MEM_RECLAIM if a wq may process work items
+ which are used during memory reclaim. Each wq with WQ_MEM_RECLAIM
+ set has an execution context reserved for it. If there is
+ dependency among multiple work items used during memory reclaim,
+ they should be queued to separate wq each with WQ_MEM_RECLAIM.
* Unless strict ordering is required, there is no need to use ST wq.
@@ -368,12 +368,13 @@ If q1 has WQ_CPU_INTENSIVE set,
recommended. In most use cases, concurrency level usually stays
well under the default limit.
-* A wq serves as a domain for forward progress guarantee (WQ_RESCUER),
- flush and work item attributes. Work items which are not involved
- in memory reclaim and don't need to be flushed as a part of a group
- of work items, and don't require any special attribute, can use one
- of the system wq. There is no difference in execution
- characteristics between using a dedicated wq and a system wq.
+* A wq serves as a domain for forward progress guarantee
+ (WQ_MEM_RECLAIM, flush and work item attributes. Work items which
+ are not involved in memory reclaim and don't need to be flushed as a
+ part of a group of work items, and don't require any special
+ attribute, can use one of the system wq. There is no difference in
+ execution characteristics between using a dedicated wq and a system
+ wq.
* Unless work items are expected to consume a huge amount of CPU
cycles, using a bound wq is usually beneficial due to the increased