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-rw-r--r--Documentation/trace/histogram.rst54
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::