perf ftrace: Add support for trace option tracing_thresh

This adds an option '--graph-opts thresh' to setup trace duration
threshold for funcgraph tracer.

  $ sudo ./perf ftrace -G '*' --graph-opts thresh=100
   3) ! 184.060 us  |    } /* schedule */
   3) ! 185.600 us  |  } /* exit_to_usermode_loop */
   2) ! 225.989 us  |    } /* schedule_idle */
   2) # 4140.051 us |  } /* do_idle */
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: http://lore.kernel.org/lkml/20200808023141.14227-14-changbin.du@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-ftrace.txt

@@ -107,6 +107,7 @@ OPTIONS
 	  nosleep-time - Measure on-CPU time only for function_graph tracer.
 	  noirqs       - Ignore functions that happen inside interrupt.
 	  verbose      - Show process names, PIDs, timestamps, etc.
+	  thresh=<n>   - Setup trace duration threshold in microseconds.
 
 SEE ALSO
 --------

tools/perf/builtin-ftrace.c

@@ -48,6 +48,7 @@ struct perf_ftrace {
 	int			graph_nosleep_time;
 	int			graph_noirqs;
 	int			graph_verbose;
+	int			graph_thresh;
 };
 
 struct filter_entry {
@@ -234,6 +235,9 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
 	if (write_tracing_file("max_graph_depth", "0") < 0)
 		return -1;
 
+	if (write_tracing_file("tracing_thresh", "0") < 0)
+		return -1;
+
 	reset_tracing_filters();
 	reset_tracing_options(ftrace);
 	return 0;
@@ -446,6 +450,20 @@ static int set_tracing_funcgraph_verbose(struct perf_ftrace *ftrace)
 	return 0;
 }
 
+static int set_tracing_thresh(struct perf_ftrace *ftrace)
+{
+	int ret;
+
+	if (ftrace->graph_thresh == 0)
+		return 0;
+
+	ret = write_tracing_file_int("tracing_thresh", ftrace->graph_thresh);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
 static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 {
 	char *trace_file;
@@ -545,6 +563,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_reset;
 	}
 
+	if (set_tracing_thresh(ftrace) < 0) {
+		pr_err("failed to set tracing thresh\n");
+		goto out_reset;
+	}
+
 	if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
 		pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
 		goto out_reset;
@@ -727,6 +750,7 @@ static int parse_graph_tracer_opts(const struct option *opt,
 		{ .name = "nosleep-time",	.value_ptr = &ftrace->graph_nosleep_time },
 		{ .name = "noirqs",		.value_ptr = &ftrace->graph_noirqs },
 		{ .name = "verbose",		.value_ptr = &ftrace->graph_verbose },
+		{ .name = "thresh",		.value_ptr = &ftrace->graph_thresh },
 		{ .name = NULL, }
 	};
 
@@ -798,7 +822,7 @@ int cmd_ftrace(int argc, const char **argv)
 	OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
 		    "Max depth for function graph tracer"),
 	OPT_CALLBACK(0, "graph-opts", &ftrace, "options",
-		     "graph tracer options, available options: nosleep-time,noirqs,verbose",
+		     "graph tracer options, available options: nosleep-time,noirqs,verbose,thresh=<n>",
 		     parse_graph_tracer_opts),
 	OPT_CALLBACK('m', "buffer-size", &ftrace.percpu_buffer_size, "size",
 		     "size of per cpu buffer", parse_buffer_size),