Commit 26f25564 authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt
Browse files

tracing/README: Add event file usage to tracing mini-HOWTO 

It would be useful to have a cheat-sheet for everything under
tracing/events/ alongside the existing text describing the other files
in the tracing/ dir.

Add short descriptions of the directories and files under events/
along with examples, similar to the existing text for the other files
in tracing/.

Also clean up a few minor alignment problems noticed when adding the
new text.

Link: http://lkml.kernel.org/r/1389993104.3040.445.camel@empanada



Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 92fdd98c

kernel/trace/trace.c

+34 −3
Original line number Diff line number Diff line
@@ -3573,6 +3573,37 @@ static const char readme_msg[] = 
	"  stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace traces\n"

#endif

#endif /* CONFIG_STACK_TRACER */

	"  events/\t\t- Directory containing all trace event subsystems:\n"

	"      enable\t\t- Write 0/1 to enable/disable tracing of all events\n"

	"  events/<system>/\t- Directory containing all trace events for <system>:\n"

	"      enable\t\t- Write 0/1 to enable/disable tracing of all <system> events\n"

	"      filter\t\t- If set, only events passing filter are traced\n"

	"  events/<system>/<event>/\t- Directory containing control files for <event>:\n"

	"      enable\t\t- Write 0/1 to enable/disable tracing of <event>\n"

	"      filter\t\t- If set, only events passing filter are traced\n"

	"      trigger\t\t- If set, a command to perform when event is hit\n"

	"            Format: <trigger>[:count][if <filter>]\n"

	"           trigger: traceon, traceoff\n"

	"                    enable_event:<system>:<event>\n"

	"                    disable_event:<system>:<event>\n"

#ifdef CONFIG_STACKTRACE

	"                    stacktrace\n"

#endif

#ifdef CONFIG_TRACER_SNAPSHOT

	"                    snapshot\n"

#endif

	"           example: echo traceoff > events/block/block_unplug/trigger\n"

	"                    echo traceoff:3 > events/block/block_unplug/trigger\n"

	"                    echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > events/block/block_unplug/trigger\n"

	"           The first disables tracing every time block_unplug is hit.\n"

	"           The second disables tracing the first 3 times block_unplug is hit.\n"

	"           The third enables the kmalloc event the first 3 times block_unplug\n"

	"             is hit and has value of greater than 1 for the 'nr_rq' event field.\n"

	"           To remove a trigger without a count:\n"

	"             echo '!<trigger> > <system>/<event>/trigger\n"

	"           To remove a trigger with a count:\n"

	"             echo '!<trigger>:0 > <system>/<event>/trigger\n"

	"           Filters can be ignored when removing a trigger.\n"

;



static ssize_t

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