Documentation/trace/hwlat_detector.rst

2 Hardware Latency Detector
6 -------------
24 The hardware latency detector works by hogging one of the cpus for configurable
31 Note that the hwlat detector should *NEVER* be used in a production environment.
36 ------
40 redefine the threshold in microseconds (us) above which latency spikes will
50   - width - time period to sample with CPUs held (usecs)
52   - window - total period of sampling, width being inside (usecs)
55 for every 1,000,000 usecs (1s) the hwlat detector will spin for 500,000 usecs
57 change to a default of 10 usecs. If any latencies that exceed the threshold is
64 If tracing_thresh was zero when hwlat detector was started, it will be set
66 tracing_thresh that hwlat detector had will be saved and this value will
67 be restored in tracing_thresh if it is still zero when hwlat detector is
74  - tracing_threshold	- minimum latency value to be considered (usecs)
75  - tracing_max_latency	- maximum hardware latency actually observed (usecs)
76  - tracing_cpumask	- the CPUs to move the hwlat thread across
77  - hwlat_detector/width	- specified amount of time to spin within window (usecs)
78  - hwlat_detector/window	- amount of time between (width) runs (usecs)
79  - hwlat_detector/mode	- the thread mode
81 By default, one hwlat detector's kernel thread will migrate across each CPU
82 specified in cpumask at the beginning of a new window, in a round-robin
86  - none:        do not force migration
87  - round-robin: migrate across each CPU specified in cpumask [default]
88  - per-cpu:     create one thread for each cpu in tracing_cpumask