[PATCH 03/19] perf ftrace: select function/function_graph tracer automatically

[Changbin Du <changbin.du@gmail.com>]

The '-g/-G' options have already implied function_graph tracer should be
used instead of function tracer. So the extra option '--tracer' can be
killed.

This patch changes the behavior as below:
  - By default, function tracer is used.
  - If '-g' or '-G' option is on, then function_graph tracer is used.
  - The perf configuration item 'ftrace.tracer' is removed.
  - The default filter for -G is to trace all functions.

Here are some examples.

This will start tracing all functions using function tracer:
  $ sudo perf ftrace

This will trace all functions using function graph tracer:
  $ sudo perf ftrace -G

This will trace function vfs_read using function graph tracer:
  $ sudo perf ftrace -G vfs_read

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 tools/perf/Documentation/perf-config.txt |  5 ---
 tools/perf/builtin-ftrace.c              | 39 ++++++------------------
 2 files changed, 9 insertions(+), 35 deletions(-)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index f16d8a71d3f5..fad6c48ed76a 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -612,11 +612,6 @@ trace.*::
 		"libbeauty", the default, to use the same argument beautifiers used in the
 		strace-like sys_enter+sys_exit lines.
 
-ftrace.*::
-	ftrace.tracer::
-		Can be used to select the default tracer. Possible values are
-		'function' and 'function_graph'.
-
 llvm.*::
 	llvm.clang-path::
 		Path to clang. If omit, search it from $PATH.
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 5584f8dec25d..57e656c35d28 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -27,7 +27,7 @@
 #include "util/cap.h"
 #include "util/config.h"
 
-#define DEFAULT_TRACER  "function_graph"
+#define DEFAULT_TRACER  "function"
 
 struct perf_ftrace {
 	struct evlist		*evlist;
@@ -408,26 +408,6 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 	return (done && !workload_exec_errno) ? 0 : -1;
 }
 
-static int perf_ftrace_config(const char *var, const char *value, void *cb)
-{
-	struct perf_ftrace *ftrace = cb;
-
-	if (!strstarts(var, "ftrace."))
-		return 0;
-
-	if (strcmp(var, "ftrace.tracer"))
-		return -1;
-
-	if (!strcmp(value, "function_graph") ||
-	    !strcmp(value, "function")) {
-		ftrace->tracer = value;
-		return 0;
-	}
-
-	pr_err("Please select \"function_graph\" (default) or \"function\"\n");
-	return -1;
-}
-
 static int parse_filter_func(const struct option *opt, const char *str,
 			     int unset __maybe_unused)
 {
@@ -467,8 +447,6 @@ int cmd_ftrace(int argc, const char **argv)
 		NULL
 	};
 	const struct option ftrace_options[] = {
-	OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
-		   "tracer to use: function_graph(default) or function"),
 	OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
 		   "trace on existing process id"),
 	OPT_INCR('v', "verbose", &verbose,
@@ -481,10 +459,12 @@ int cmd_ftrace(int argc, const char **argv)
 		     "trace given functions only", parse_filter_func),
 	OPT_CALLBACK('N', "notrace-funcs", &ftrace.notrace, "func",
 		     "do not trace given functions", parse_filter_func),
-	OPT_CALLBACK('G', "graph-funcs", &ftrace.graph_funcs, "func",
-		     "Set graph filter on given functions", parse_filter_func),
+	OPT_CALLBACK_DEFAULT('G', "graph-funcs", &ftrace.graph_funcs, "func",
+		     "Set graph filter on given functions (imply to use function_graph tracer)",
+		     parse_filter_func, "*"),
 	OPT_CALLBACK('g', "nograph-funcs", &ftrace.nograph_funcs, "func",
-		     "Set nograph filter on given functions", parse_filter_func),
+		     "Set nograph filter on given functions (imply to use function_graph tracer)",
+		     parse_filter_func),
 	OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
 		    "Max depth for function graph tracer"),
 	OPT_END()
@@ -495,15 +475,14 @@ int cmd_ftrace(int argc, const char **argv)
 	INIT_LIST_HEAD(&ftrace.graph_funcs);
 	INIT_LIST_HEAD(&ftrace.nograph_funcs);
 
-	ret = perf_config(perf_ftrace_config, &ftrace);
-	if (ret < 0)
-		return -1;
-
 	argc = parse_options(argc, argv, ftrace_options, ftrace_usage,
 			    PARSE_OPT_STOP_AT_NON_OPTION);
 	if (!argc && target__none(&ftrace.target))
 		ftrace.target.system_wide = true;
 
+	if (!list_empty(&ftrace.graph_funcs) || !list_empty(&ftrace.nograph_funcs))
+		ftrace.tracer = "function_graph";
+
 	ret = target__validate(&ftrace.target);
 	if (ret) {
 		char errbuf[512];
-- 
2.25.1