tracing: add support for userspace stacktraces in tracing/iter_ctrl
Impact: add new (default-off) tracing visualization feature
Usage example:
mount -t debugfs nodev /sys/kernel/debug
cd /sys/kernel/debug/tracing
echo userstacktrace >iter_ctrl
echo sched_switch >current_tracer
echo 1 >tracing_enabled
.... run application ...
echo 0 >tracing_enabled
Then read one of 'trace','latency_trace','trace_pipe'.
To get the best output you can compile your userspace programs with
frame pointers (at least glibc + the app you are tracing).
Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index 753f4de..79a80f7 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -324,7 +324,7 @@
cat /debug/tracing/trace_options
print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \
- noblock nostacktrace nosched-tree
+ noblock nostacktrace nosched-tree nouserstacktrace
To disable one of the options, echo in the option prepended with "no".
@@ -378,6 +378,9 @@
When a trace is recorded, so is the stack of functions.
This allows for back traces of trace sites.
+ userstacktrace - This option changes the trace.
+ It records a stacktrace of the current userspace thread.
+
sched-tree - TBD (any users??)