mirror of
https://github.com/torvalds/linux.git
synced 2024-11-16 00:52:01 +00:00
143c145e3a
- fix some typos - document the difference between '>' and '>>' - document the 'enable' toggle - remove section "Defining an event-enabled tracepoint", since it's out-dated and sample/trace_events/ already serves this purpose. v2: add "Updated by Li Zefan" [ Impact: make documentation up-to-date ] Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: "Theodore Ts'o" <tytso@mit.edu> LKML-Reference: <4A125503.5060406@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
91 lines
2.6 KiB
Plaintext
91 lines
2.6 KiB
Plaintext
Event Tracing
|
|
|
|
Documentation written by Theodore Ts'o
|
|
Updated by Li Zefan
|
|
|
|
1. Introduction
|
|
===============
|
|
|
|
Tracepoints (see Documentation/trace/tracepoints.txt) can be used
|
|
without creating custom kernel modules to register probe functions
|
|
using the event tracing infrastructure.
|
|
|
|
Not all tracepoints can be traced using the event tracing system;
|
|
the kernel developer must provide code snippets which define how the
|
|
tracing information is saved into the tracing buffer, and how the
|
|
tracing information should be printed.
|
|
|
|
2. Using Event Tracing
|
|
======================
|
|
|
|
2.1 Via the 'set_event' interface
|
|
---------------------------------
|
|
|
|
The events which are available for tracing can be found in the file
|
|
/debug/tracing/available_events.
|
|
|
|
To enable a particular event, such as 'sched_wakeup', simply echo it
|
|
to /debug/tracing/set_event. For example:
|
|
|
|
# echo sched_wakeup >> /debug/tracing/set_event
|
|
|
|
[ Note: '>>' is necessary, otherwise it will firstly disable
|
|
all the events. ]
|
|
|
|
To disable an event, echo the event name to the set_event file prefixed
|
|
with an exclamation point:
|
|
|
|
# echo '!sched_wakeup' >> /debug/tracing/set_event
|
|
|
|
To disable all events, echo an empty line to the set_event file:
|
|
|
|
# echo > /debug/tracing/set_event
|
|
|
|
To enable all events, echo '*:*' or '*:' to the set_event file:
|
|
|
|
# echo *:* > /debug/tracing/set_event
|
|
|
|
The events are organized into subsystems, such as ext4, irq, sched,
|
|
etc., and a full event name looks like this: <subsystem>:<event>. The
|
|
subsystem name is optional, but it is displayed in the available_events
|
|
file. All of the events in a subsystem can be specified via the syntax
|
|
"<subsystem>:*"; for example, to enable all irq events, you can use the
|
|
command:
|
|
|
|
# echo 'irq:*' > /debug/tracing/set_event
|
|
|
|
2.2 Via the 'enable' toggle
|
|
---------------------------
|
|
|
|
The events available are also listed in /debug/tracing/events/ hierarchy
|
|
of directories.
|
|
|
|
To enable event 'sched_wakeup':
|
|
|
|
# echo 1 > /debug/tracing/events/sched/sched_wakeup/enable
|
|
|
|
To disable it:
|
|
|
|
# echo 0 > /debug/tracing/events/sched/sched_wakeup/enable
|
|
|
|
To enable all events in sched subsystem:
|
|
|
|
# echo 1 > /debug/tracing/events/sched/enable
|
|
|
|
To eanble all events:
|
|
|
|
# echo 1 > /debug/tracing/events/enable
|
|
|
|
When reading one of these enable files, there are four results:
|
|
|
|
0 - all events this file affects are disabled
|
|
1 - all events this file affects are enabled
|
|
X - there is a mixture of events enabled and disabled
|
|
? - this file does not affect any event
|
|
|
|
3. Defining an event-enabled tracepoint
|
|
=======================================
|
|
|
|
See The example provided in samples/trace_events
|
|
|