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Diffstat (limited to 'Documentation/trace/histogram.rst')
| -rw-r--r-- | Documentation/trace/histogram.rst | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index f95d94d19c22..ddbaffa530f9 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -1915,7 +1915,10 @@ The following commonly-used handler.action pairs are available: The 'matching.event' specification is simply the fully qualified event name of the event that matches the target event for the - onmatch() functionality, in the form 'system.event_name'. + onmatch() functionality, in the form 'system.event_name'. Histogram + keys of both events are compared to find if events match. In case + multiple histogram keys are used, they all must match in the specified + order. Finally, the number and type of variables/fields in the 'param list' must match the number and types of the fields in the @@ -1978,9 +1981,9 @@ The following commonly-used handler.action pairs are available: /sys/kernel/debug/tracing/events/sched/sched_waking/trigger Then, when the corresponding thread is actually scheduled onto the - CPU by a sched_switch event, calculate the latency and use that - along with another variable and an event field to generate a - wakeup_latency synthetic event:: + CPU by a sched_switch event (saved_pid matches next_pid), calculate + the latency and use that along with another variable and an event field + to generate a wakeup_latency synthetic event:: # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\ onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,\ |