[PATCH v3 01/17] 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 marked as deprecated.
  - The option '--tracer' is marked as deprecated.

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>

---
v3: remove default '*' for -G/-T.
---
 tools/perf/Documentation/perf-config.txt |  5 -----
 tools/perf/Documentation/perf-ftrace.txt |  2 +-
 tools/perf/builtin-ftrace.c              | 15 ++++++++++-----
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index c7d3df5798e2..a25fee7de3b2 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/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index b80c84307dc9..952e46669168 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -24,7 +24,7 @@ OPTIONS
 
 -t::
 --tracer=::
-	Tracer to use: function_graph or function.
+	Tracer to use: function_graph or function. This option is deprecated.
 
 -v::
 --verbose=::
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 2bfc1b0db536..5f53da87040d 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -27,7 +27,6 @@
 #include "util/cap.h"
 #include "util/config.h"
 
-#define DEFAULT_TRACER  "function_graph"
 
 struct perf_ftrace {
 	struct evlist		*evlist;
@@ -419,6 +418,7 @@ static int perf_ftrace_config(const char *var, const char *value, void *cb)
 	if (strcmp(var, "ftrace.tracer"))
 		return -1;
 
+	pr_warning("Configuration ftrace.tracer is deprecated\n");
 	if (!strcmp(value, "function_graph") ||
 	    !strcmp(value, "function")) {
 		ftrace->tracer = value;
@@ -459,7 +459,7 @@ int cmd_ftrace(int argc, const char **argv)
 {
 	int ret;
 	struct perf_ftrace ftrace = {
-		.tracer = DEFAULT_TRACER,
+		.tracer = "function",
 		.target = { .uid = UINT_MAX, },
 	};
 	const char * const ftrace_usage[] = {
@@ -469,7 +469,7 @@ int cmd_ftrace(int argc, const char **argv)
 	};
 	const struct option ftrace_options[] = {
 	OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
-		   "tracer to use: function_graph(default) or function"),
+		   "tracer to use: function or function_graph (This option is deprecated)"),
 	OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
 		   "trace on existing process id"),
 	OPT_INCR('v', "verbose", &verbose,
@@ -479,11 +479,13 @@ int cmd_ftrace(int argc, const char **argv)
 	OPT_STRING('C', "cpu", &ftrace.target.cpu_list, "cpu",
 		    "list of cpus to monitor"),
 	OPT_CALLBACK('T', "trace-funcs", &ftrace.filters, "func",
-		     "trace given functions only", parse_filter_func),
+		     "trace given functions using function tracer",
+		     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),
+		     "trace given functions using function_graph tracer",
+		     parse_filter_func),
 	OPT_CALLBACK('g', "nograph-funcs", &ftrace.nograph_funcs, "func",
 		     "Set nograph filter on given functions", parse_filter_func),
 	OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
@@ -505,6 +507,9 @@ int cmd_ftrace(int argc, const char **argv)
 	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