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Code Issues Releases Wiki Activity

workqueue: Track and monitor per-workqueue CPU time usage 

Now that wq_worker_tick() is there, we can easily track the rough CPU time
consumption of each workqueue by charging the whole tick whenever a tick
hits an active workqueue. While not super accurate, it provides reasonable
visibility into the workqueues that consume a lot of CPU cycles.
wq_monitor.py is updated to report the per-workqueue CPU times.

v2: wq_monitor.py was using "cputime" as the key when outputting in json
    format. Use "cpu_time" instead for consistency with other fields.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2023-05-17 17:02:09 -10:00
parent 6363845005
commit 8a1dd1e547
3 changed files with 29 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
Documentation/core-api/workqueue.rst
View File

@ -354,25 +354,25 @@ Monitoring
Use tools/workqueue/wq_monitor.py to monitor workqueue operations: ::
$ tools/workqueue/wq_monitor.py events
total infl CPUitsv CMwake mayday rescued
events 18545 0 0 5 - -
events_highpri 8 0 0 0 - -
events_long 3 0 0 0 - -
events_unbound 38306 0 - - - -
events_freezable 0 0 0 0 - -
events_power_efficient 29598 0 0 0 - -
events_freezable_power_ 10 0 0 0 - -
sock_diag_events 0 0 0 0 - -
total infl CPUtime CPUhog CMwake mayday rescued
events 18545 0 6.1 0 5 - -
events_highpri 8 0 0.0 0 0 - -
events_long 3 0 0.0 0 0 - -
events_unbound 38306 0 0.1 - - - -
events_freezable 0 0 0.0 0 0 - -
events_power_efficient 29598 0 0.2 0 0 - -
events_freezable_power_ 10 0 0.0 0 0 - -
sock_diag_events 0 0 0.0 0 0 - -
total infl CPUitsv CMwake mayday rescued
events 18548 0 0 5 - -
events_highpri 8 0 0 0 - -
events_long 3 0 0 0 - -
events_unbound 38322 0 - - - -
events_freezable 0 0 0 0 - -
events_power_efficient 29603 0 0 0 - -
events_freezable_power_ 10 0 0 0 - -
sock_diag_events 0 0 0 0 - -
total infl CPUtime CPUhog CMwake mayday rescued
events 18548 0 6.1 0 5 - -
events_highpri 8 0 0.0 0 0 - -
events_long 3 0 0.0 0 0 - -
events_unbound 38322 0 0.1 - - - -
events_freezable 0 0 0.0 0 0 - -
events_power_efficient 29603 0 0.2 0 0 - -
events_freezable_power_ 10 0 0.0 0 0 - -
sock_diag_events 0 0 0.0 0 0 - -
...

3
kernel/workqueue.c
View File

@ -212,6 +212,7 @@ struct worker_pool {
enum pool_workqueue_stats {
PWQ_STAT_STARTED, /* work items started execution */
PWQ_STAT_COMPLETED, /* work items completed execution */
PWQ_STAT_CPU_TIME, /* total CPU time consumed */
PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
PWQ_STAT_MAYDAY, /* maydays to rescuer */
@ -1136,6 +1137,8 @@ void wq_worker_tick(struct task_struct *task)
if (!pwq)
return;
pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
/*
* If the current worker is concurrency managed and hogged the CPU for
* longer than wq_cpu_intensive_thresh_us, it's automatically marked

9
tools/workqueue/wq_monitor.py
View File

@ -11,6 +11,10 @@ https://github.com/osandov/drgn.
infl The number of currently in-flight work items.
CPUtime Total CPU time consumed by the workqueue in seconds. This is
sampled from scheduler ticks and only provides ballpark
measurement. "nohz_full=" CPUs are excluded from measurement.
CPUitsv The number of times a concurrency-managed work item hogged CPU
longer than the threshold (workqueue.cpu_intensive_thresh_us)
and got excluded from concurrency management to avoid stalling
@ -58,6 +62,7 @@ WQ_MEM_RECLAIM = prog['WQ_MEM_RECLAIM']
PWQ_STAT_STARTED = prog['PWQ_STAT_STARTED'] # work items started execution
PWQ_STAT_COMPLETED = prog['PWQ_STAT_COMPLETED'] # work items completed execution
PWQ_STAT_CPU_TIME = prog['PWQ_STAT_CPU_TIME'] # total CPU time consumed
PWQ_STAT_CPU_INTENSIVE = prog['PWQ_STAT_CPU_INTENSIVE'] # wq_cpu_intensive_thresh_us violations
PWQ_STAT_CM_WAKEUP = prog['PWQ_STAT_CM_WAKEUP'] # concurrency-management worker wakeups
PWQ_STAT_MAYDAY = prog['PWQ_STAT_MAYDAY'] # maydays to rescuer
@ -81,13 +86,14 @@ class WqStats:
'mem_reclaim' : self.mem_reclaim,
'started' : self.stats[PWQ_STAT_STARTED],
'completed' : self.stats[PWQ_STAT_COMPLETED],
'cpu_time' : self.stats[PWQ_STAT_CPU_TIME],
'cpu_intensive' : self.stats[PWQ_STAT_CPU_INTENSIVE],
'cm_wakeup' : self.stats[PWQ_STAT_CM_WAKEUP],
'mayday' : self.stats[PWQ_STAT_MAYDAY],
'rescued' : self.stats[PWQ_STAT_RESCUED], }
def table_header_str():
return f'{"":>24} {"total":>8} {"infl":>5} '\
return f'{"":>24} {"total":>8} {"infl":>5} {"CPUtime":>8} '\
f'{"CPUitsv":>7} {"CMwake":>7} {"mayday":>7} {"rescued":>7}'
def table_row_str(self):
@ -107,6 +113,7 @@ class WqStats:
out = f'{self.name[-24:]:24} ' \
f'{self.stats[PWQ_STAT_STARTED]:8} ' \
f'{max(self.stats[PWQ_STAT_STARTED] - self.stats[PWQ_STAT_COMPLETED], 0):5} ' \
f'{self.stats[PWQ_STAT_CPU_TIME] / 1000000:8.1f} ' \
f'{cpu_intensive:>7} ' \
f'{cm_wakeup:>7} ' \
f'{mayday:>7} ' \