Re: [for-next][PATCH 9/9] tracing: Update debugfs README file

[Keun-O Park]

On Mon, Mar 18, 2013 at 5:22 PM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> Hi Steve,
>
> On Fri, 15 Mar 2013 23:24:21 -0400, Steven Rostedt wrote:
>> From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
>>
>> Update the README file in debugfs/tracing to something more useful.
>> What's currently in the file is very old and what it shows doesn't
>> have much use. Heck, it tells you how to mount debugfs! But to read
>> this file you would have already needed to mount it.
>>
>> Replace the file with current up-to-date information. It's rather
>> limited, but what do you expect from a pseudo README file.
>>
>> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
>> ---
>>  kernel/trace/trace.c |   89 ++++++++++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 75 insertions(+), 14 deletions(-)
>>
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index 3dc7999..83ad596 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -3300,20 +3300,81 @@ static const struct file_operations tracing_iter_fops = {
>>
>>  static const char readme_msg[] =
>>       "tracing mini-HOWTO:\n\n"
>> -     "# mount -t debugfs nodev /sys/kernel/debug\n\n"
>> -     "# cat /sys/kernel/debug/tracing/available_tracers\n"
>> -     "wakeup wakeup_rt preemptirqsoff preemptoff irqsoff function nop\n\n"
>> -     "# cat /sys/kernel/debug/tracing/current_tracer\n"
>> -     "nop\n"
>> -     "# echo wakeup > /sys/kernel/debug/tracing/current_tracer\n"
>> -     "# cat /sys/kernel/debug/tracing/current_tracer\n"
>> -     "wakeup\n"
>> -     "# cat /sys/kernel/debug/tracing/trace_options\n"
>> -     "noprint-parent nosym-offset nosym-addr noverbose\n"
>> -     "# echo print-parent > /sys/kernel/debug/tracing/trace_options\n"
>> -     "# echo 1 > /sys/kernel/debug/tracing/tracing_on\n"
>> -     "# cat /sys/kernel/debug/tracing/trace > /tmp/trace.txt\n"
>> -     "# echo 0 > /sys/kernel/debug/tracing/tracing_on\n"
>> +     "# echo 0 > tracing_on : quick way to disable tracing\n"
>> +     "# echo 1 > tracing_on : quick way to re-enable tracing\n\n"
>> +     " Important files:\n"
>> +     "  trace\t\t\t- The static contents of the buffer\n"
>> +     "\t\t\t  To clear the buffer write into this file: echo > trace\n"
>> +     "  trace_pipe\t\t- A consuming read to see the contents of the buffer\n"
>> +     "  current_tracer\t- function and latency tracers\n"
>> +     "  available_tracers\t- list of configured tracers for current_tracer\n"
>> +     "  buffer_size_kb\t- view and modify size of per cpu buffer\n"
>> +     "  buffer_total_size_kb  - view total size of all cpu buffers\n\n"
>> +     "  trace_clock\t\t-change the clock used to order events\n"
>> +     "       local:   Per cpu clock but may not be synced across CPUS\n"
>> +     "      global:   Synced across CPUs but slows tracing down.\n"
>> +     "     counter:   Not a clock, but just an increment\n"
>> +     "      uptime:   Jiffy counter from time of boot\n"
>> +     "        perf:   Same clock that perf events use\n"
>> +#ifdef CONFIG_X86_64
>> +     "     x86-tsc:   TSC cycle counter\n"
>> +#endif
>> +     "\n  trace_marker\t\t- Writes into this file writes into the kernel buffer\n"
>> +     "  tracing_cpumask\t- Limit which CPUs to trace\n"
>> +     "  instances\t\t- Make sub-buffers with: mkdir instances/foo\n"
>> +     "\t\t\t  Remove sub-buffer with rmdir\n"
>> +     "  trace_options\t\t- Set format or modify how tracing happens\n"
>> +     "\t\t\t  Disable an option by adding a suffix 'no' to the option name\n"
>> +#ifdef CONFIG_DYNAMIC_FTRACE
>> +     "\n  available_filter_functions - list of functions that can be filtered on\n"
>> +     "  set_ftrace_filter\t- echo function name in here to only trace these functions\n"
>> +     "            accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
>> +     "            modules: Can select a group via module\n"
>> +     "             Format: :mod:<module-name>\n"
>> +     "             example: echo :mod:ext3 > set_ftrace_filter\n"
>> +     "            triggers: a command to perform when function is hit\n"
>> +     "              Format: <function>:<trigger>[:count]\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 do_fault:traceoff > set_ftrace_filter\n"
>> +     "                      echo do_trap:traceoff:3 > set_ftrace_filter\n"
>> +     "             The first one will disable tracing everytime do_fault is hit\n"
>> +     "             The second will disable tracing at most 3 times whne do_trap is hit\n"
>
> s/whne/when/
>
> It's slightly confusing for me to read the "at most" part.  Did you mean
> it by "The second will disable tracing after do_trace is hit 3 times"?
>
> Thanks,
> Namhyung
>
>
>> +     "             To remove trigger without count:\n"
>> +     "               echo '!<function>:<trigger> > set_ftrace_filter\n"
>> +     "             To remove trigger with a count:\n"
>> +     "               echo '!<function>:<trigger>:0 > set_ftrace_filter\n"
>> +     "  set_ftrace_notrace\t- echo function name in here to never trace.\n"
>> +     "            accepts: func_full_name, *func_end, func_begin*, *func_middle*\n"
>> +     "            modules: Can select a group via module command :mod:\n"
>> +     "            Does not accept triggers\n"
>> +#endif /* CONFIG_DYNAMIC_FTRACE */
>> +#ifdef CONFIG_FUNCTION_TRACER
>> +     "  set_ftrace_pid\t- Write pid(s) to only function trace those pids (function)\n"
>> +#endif
>> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> +     "  set_graph_function\t- Trace the nested calls of a function (function_graph)\n"
>> +     "  max_graph_depth\t- Trace a limited depth of nested calls (0 is unlimited)\n"
>> +#endif
>> +#ifdef CONFIG_TRACER_SNAPSHOT
>> +     "\n  snashot\t\t- Like 'trace' but shows the content of the static snapshot buffer\n"
>> +     "\t\t\t  Read the contents for more infromation\n"
>> +#endif

There're two more typos.
s/snashot/snapshot/
s/infromation/information/


>> +#ifdef CONFIG_STACKTRACE
>> +     "  stack_trace\t\t- Shows the max stack trace when active\n"
>> +     "  stack_max_size\t- Shows current max stack size that was traced\n"
>> +     "\t\t\t  Write into this file to reset the max size (trigger a new trace)\n"
>> +#ifdef CONFIG_DYNAMIC_FTRACE
>> +     "  stack_trace_filter\t- Like set_ftrace_filter but limits what stack_trace traces\n"
>> +#endif
>> +#endif /* CONFIG_STACKTRACE */
>>  ;
>>
>>  static ssize_t
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