diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/histogram.rst | 54 |
1 files changed, 37 insertions, 17 deletions
diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index 79476c906b1a..0ea59d45aef1 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -1873,31 +1873,45 @@ The available handlers are: The available actions are: - - <synthetic_event_name>(param list) - generate synthetic event + - trace(<synthetic_event_name>,param list) - generate synthetic event - save(field,...) - save current event fields - snapshot() - snapshot the trace buffer The following commonly-used handler.action pairs are available: - - onmatch(matching.event).<synthetic_event_name>(param list) + - onmatch(matching.event).trace(<synthetic_event_name>,param list) - The 'onmatch(matching.event).<synthetic_event_name>(params)' hist - trigger action is invoked whenever an event matches and the - histogram entry would be added or updated. It causes the named - synthetic event to be generated with the values given in the + The 'onmatch(matching.event).trace(<synthetic_event_name>,param + list)' hist trigger action is invoked whenever an event matches + and the histogram entry would be added or updated. It causes the + named synthetic event to be generated with the values given in the 'param list'. The result is the generation of a synthetic event that consists of the values contained in those variables at the - time the invoking event was hit. - - The 'param list' consists of one or more parameters which may be - either variables or fields defined on either the 'matching.event' - or the target event. The variables or fields specified in the - param list may be either fully-qualified or unqualified. If a - variable is specified as unqualified, it must be unique between - the two events. A field name used as a param can be unqualified - if it refers to the target event, but must be fully qualified if - it refers to the matching event. A fully-qualified name is of the - form 'system.event_name.$var_name' or 'system.event_name.field'. + time the invoking event was hit. For example, if the synthetic + event name is 'wakeup_latency', a wakeup_latency event is + generated using onmatch(event).trace(wakeup_latency,arg1,arg2). + + There is also an equivalent alternative form available for + generating synthetic events. In this form, the synthetic event + name is used as if it were a function name. For example, using + the 'wakeup_latency' synthetic event name again, the + wakeup_latency event would be generated by invoking it as if it + were a function call, with the event field values passed in as + arguments: onmatch(event).wakeup_latency(arg1,arg2). The syntax + for this form is: + + onmatch(matching.event).<synthetic_event_name>(param list) + + In either case, the 'param list' consists of one or more + parameters which may be either variables or fields defined on + either the 'matching.event' or the target event. The variables or + fields specified in the param list may be either fully-qualified + or unqualified. If a variable is specified as unqualified, it + must be unique between the two events. A field name used as a + param can be unqualified if it refers to the target event, but + must be fully qualified if it refers to the matching event. A + fully-qualified name is of the form 'system.event_name.$var_name' + or 'system.event_name.field'. The 'matching.event' specification is simply the fully qualified event name of the event that matches the target event for the @@ -1928,6 +1942,12 @@ The following commonly-used handler.action pairs are available: wakeup_new_test($testpid) if comm=="cyclictest"' >> \ /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger + Or, equivalently, using the 'trace' keyword syntax: + + # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\ + trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \ + /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger + Creating and displaying a histogram based on those events is now just a matter of using the fields and new synthetic event in the tracing/events/synthetic directory, as usual:: |