[PATCH 13/19] perf ftrace: add option '-b/--buffer-size' to set per-cpu buffer size

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

This adds an option '-b/--buffer-size' to allow us set the size of per-cpu
tracing buffer.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 tools/perf/builtin-ftrace.c | 45 ++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 8fd95c109fe8..a93fbdac6aa4 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -47,6 +47,7 @@ struct perf_ftrace {
 	bool			long_info;
 	unsigned		tracing_thresh;
 	bool			trace_children;
+	unsigned		buffer_size_kb;
 };
 
 struct filter_entry {
@@ -187,6 +188,17 @@ static int read_tracing_file_to_stdout(const char *name)
 	return ret;
 }
 
+static int write_tracing_file_int(const char *name, int value)
+{
+	char buf[16];
+
+	snprintf(buf, sizeof(buf), "%d", value);
+	if (write_tracing_file(name, buf) < 0)
+		return -1;
+
+	return 0;
+}
+
 static int reset_tracing_cpu(void);
 static void reset_tracing_filters(void);
 
@@ -360,8 +372,6 @@ static void reset_tracing_filters(void)
 
 static int set_tracing_depth(struct perf_ftrace *ftrace)
 {
-	char buf[16];
-
 	if (ftrace->graph_depth == 0)
 		return 0;
 
@@ -370,9 +380,7 @@ static int set_tracing_depth(struct perf_ftrace *ftrace)
 		return -1;
 	}
 
-	snprintf(buf, sizeof(buf), "%d", ftrace->graph_depth);
-
-	if (write_tracing_file("max_graph_depth", buf) < 0)
+	if (write_tracing_file_int("max_graph_depth", ftrace->graph_depth) < 0)
 		return -1;
 
 	return 0;
@@ -419,14 +427,10 @@ static int set_tracing_long_info(struct perf_ftrace *ftrace)
 
 static int set_tracing_thresh(struct perf_ftrace *ftrace)
 {
-	char buf[16];
-
 	if (ftrace->tracing_thresh == 0)
 		return 0;
 
-	snprintf(buf, sizeof(buf), "%d", ftrace->tracing_thresh);
-
-	if (write_tracing_file("tracing_thresh", buf) < 0)
+	if (write_tracing_file_int("tracing_thresh", ftrace->tracing_thresh) < 0)
 		return -1;
 
 	return 0;
@@ -454,6 +458,20 @@ static int set_tracing_trace_children(struct perf_ftrace *ftrace)
 	return 0;
 }
 
+static int set_tracing_buffer_size_kb(struct perf_ftrace *ftrace)
+{
+	int ret;
+
+	if (ftrace->buffer_size_kb == 0)
+		return 0;
+
+	ret = write_tracing_file_int("buffer_size_kb", ftrace->buffer_size_kb);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
 static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 {
 	char *trace_file;
@@ -557,6 +575,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_reset;
 	}
 
+	if (set_tracing_buffer_size_kb(ftrace) < 0) {
+		pr_err("failed to set tracing per-cpu buffer size\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;
@@ -706,6 +729,8 @@ int cmd_ftrace(int argc, const char **argv)
 		     "Only show functions of which the duration is greater than <n>µs"),
 	OPT_BOOLEAN(0, "trace-children", &ftrace.trace_children,
 		    "Trace children processes"),
+	OPT_UINTEGER('b', "buffer-size", &ftrace.buffer_size_kb,
+		     "size of per cpu buffer in kb"),
 	OPT_END()
 	};
 
-- 
2.25.1