Add missing ')' and add note about the new way of triggering an event.
CC: Randy Dunlap <[email protected]>
Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Manuel Ebner <[email protected]>
---
@ Steven, I added this line, because else the references wouldn't make sense.
References: $wakeup_lat, next_pid
+ ... (which
+could equivalently be written trace(wakeup_latency,$wakeup_lat,next_pid)
are implemented, the parameters specified to the trace handler must be
variables. In this case, $wakeup_lat is obviously a variable, but
next_pid isn't, since it's just naming a field in the sched_switch
---
Documentation/trace/histogram-design.rst | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/trace/histogram-design.rst
b/Documentation/trace/histogram-design.rst
index 41a726cd3..86c83b177 100644
--- a/Documentation/trace/histogram-design.rst
+++ b/Documentation/trace/histogram-design.rst
@@ -25,7 +25,7 @@ tracing_map.c.
If the kernel is compiled with CONFIG_HIST_TRIGGERS_DEBUG set, an
event file named 'hist_debug' will appear in each event's
-subdirectory. This file can be read at any time and will display some
+
of the hist trigger internals described in this document. Specific
examples and output will be described in test cases below.
@@ -916,6 +916,13 @@ means it will be automatically converted into a field
variable::
onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,next_pid)' >>
/sys/kernel/tracing/events/sched/sched_switch/trigger
+Note that the above is the old way to trigger a synthetic event, whereas the
+newer way is preferred, which uses the trace() action handler::
+
+ # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0: \
+
onmatch(sched.sched_waking).trace(wakeup_latency,$wakeup_lat,next_pid)' >>
+ /sys/kernel/tracing/events/sched/sched_switch/trigger
+
The diagram for the sched_switch event is similar to previous examples
but shows the additional field_vars[] array for hist_data and shows
the linkages between the field_vars and the variables and references
--
2.54.0
