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authorTejun Heo <tj@kernel.org>2023-05-17 17:02:08 -1000
committerTejun Heo <tj@kernel.org>2023-05-17 17:02:08 -1000
commit725e8ec59c56c65fb92e343c10a8842cd0d4f194 (patch)
treeb357ac51c47bdc4c24f87090a0d2191a84419b81 /Documentation/core-api
parent854f5cc5b7355ceebf2bdfed97ea8f3c5d47a0c3 (diff)
workqueue: Add pwq->stats[] and a monitoring script
Currently, the only way to peer into workqueue operations is through tracing. While possible, it isn't easy or convenient to monitor per-workqueue behaviors over time this way. Let's add pwq->stats[] that track relevant events and a drgn monitoring script - tools/workqueue/wq_monitor.py. It's arguable whether this needs to be configurable. However, it currently only has several counters and the runtime overhead shouldn't be noticeable given that they're on pwq's which are per-cpu on per-cpu workqueues and per-numa-node on unbound ones. Let's keep it simple for the time being. v2: Patch reordered to earlier with fewer fields. Field will be added back gradually. Help message improved. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Diffstat (limited to 'Documentation/core-api')
-rw-r--r--Documentation/core-api/workqueue.rst32
1 files changed, 32 insertions, 0 deletions
diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst
index 8ec4d6270b24..7e5c39310bbf 100644
--- a/Documentation/core-api/workqueue.rst
+++ b/Documentation/core-api/workqueue.rst
@@ -348,6 +348,37 @@ Guidelines
level of locality in wq operations and work item execution.
+Monitoring
+==========
+
+Use tools/workqueue/wq_monitor.py to monitor workqueue operations: ::
+
+ $ tools/workqueue/wq_monitor.py events
+ total infl CMwake mayday rescued
+ events 18545 0 5 - -
+ events_highpri 8 0 0 - -
+ events_long 3 0 0 - -
+ events_unbound 38306 0 - - -
+ events_freezable 0 0 0 - -
+ events_power_efficient 29598 0 0 - -
+ events_freezable_power_ 10 0 0 - -
+ sock_diag_events 0 0 0 - -
+
+ total infl CMwake mayday rescued
+ events 18548 0 5 - -
+ events_highpri 8 0 0 - -
+ events_long 3 0 0 - -
+ events_unbound 38322 0 - - -
+ events_freezable 0 0 0 - -
+ events_power_efficient 29603 0 0 - -
+ events_freezable_power_ 10 0 0 - -
+ sock_diag_events 0 0 0 - -
+
+ ...
+
+See the command's help message for more info.
+
+
Debugging
=========
@@ -387,6 +418,7 @@ the stack trace of the offending worker thread. ::
The work item's function should be trivially visible in the stack
trace.
+
Non-reentrance Conditions
=========================