following patches add trace event support for ocfs2.
for tracepoint, see Documentation/trace/tracepoints.txt
for trace events, see Documentation/trace/events.txt
the first patch add file include/trace/events/ocfs2.h to kernel tree. it is used
to store trace declarations. it's contents are self-explained.
NOTE that each ocfs2 header file should be above "#include <linux/tracepoint.h>"
the second one is an example which adds trace event to ocfs2_file_aio_read().
NOTE that CREATE_TRACE_POINTS must be defined before including trace/event/ocfs2.h
when trace event is used.
enable/disable the trace event:
1) debugfs is need to be mount for using trace event.
mount -t debugfs debugfs /sys/kernel/debug(or somewhere else)
2) enable/disable some specific event,
echo '1'/'0'>/sys/kernel/debug/tracing/events/ocfs2/ocfs2_file_aio_read/enable
3) to see the trace log,
cat /sys/kernel/debug/tracing/trace
an output example is:
[root at cool ocfs2_file_aio_read]# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
cat-2587 [001] 708.929889: ocfs2_file_aio_read: 0xf544bed8 0xf544bf5c 1 0
cat-2587 [000] 708.944128: ocfs2_file_aio_read: 0xf544bed8 0xf544bf5c 1 43
examples of using filter.
1) if pid is 0, do the trace:
echo "common_pid == 0" >/sys/kernel/debug/tracing/events/ocfs2/ocfs2_file_aio_read/filter
2) if group id not 0, do the trace:
echo "common_tgid != 0" >filter
for filter expression, so far, see http://article.gmane.org/gmane.linux.kernel/887690?