Re: [PATCH 2/3] perf ftrace: Add ftrace.tracer config option

[Taeung Song]

Hi, Arnaldo :)

On 01/27/2017 03:58 AM, Arnaldo Carvalho de Melo wrote:

Em Thu, Jan 26, 2017 at 06:35:38PM +0900, Taeung Song escreveu:

Currently perf ftrace command will select 'function_graph' or 'function'.
So add ftrace.tracer config option to select tracer

    # cat ~/.perfconfig
    [ftrace]
        tracer = function

    # perf ftrace usleep 123456 | head -10
      <...>-14450 [002] d... 10089.284231: finish_task_switch <-__schedule
      <...>-14450 [002] .... 10089.284232: finish_wait <-pipe_wait
      <...>-14450 [002] .... 10089.284232: mutex_lock <-pipe_wait
      <...>-14450 [002] .... 10089.284232: _cond_resched <-mutex_lock
      <...>-14450 [002] .... 10089.284233: generic_pipe_buf_confirm <-pipe_read

Cc: Jiri Olsa <jo...@kernel.org>
Cc: Namhyung Kim <namhy...@kernel.org>
Signed-off-by: Taeung Song <treeze.tae...@gmail.com>
---
 tools/perf/builtin-ftrace.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 414444d..8df5416 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -17,6 +17,7 @@
 #include "evlist.h"
 #include "target.h"
 #include "thread_map.h"
+#include "util/config.h"


 #define DEFAULT_TRACER  "function_graph"
@@ -198,6 +199,23 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int 
argc, const char **argv)
        return done ? 0 : -1;
 }

+static int perf_ftrace_config(const char *var, const char *value, void *cb)
+{
+       struct perf_ftrace *ftrace = cb;
+
+       if (!strcmp(var, "ftrace.tracer")) {
+               if (!strcmp(value, "function_graph"))
+                       ftrace->tracer = DEFAULT_TRACER;
+               else if (!strcmp(value, "function"))
+                       ftrace->tracer = "function";
+               else
+                       return -1;

Please warn the user for invalid values and either just say that it is
ignoring that setting or return -1 to make perf_config() return that,
then make cmd_ftrace() check the return of perf_config() and bail out if
you're not ignoring the config value.

I think its better to do a: "pr_err()" in that "return -1" branch and
make 'perf ftrace' fail, so that the user can fix its config before
proceeding.

I understood it!
I'll modify this patch and resend it. :)

Thanks,
Taeung