[PATCH v2 08/15] perf ftrace: add option '--inherit' to trace children processes

From: Changbin Du
Date: Sat Jun 27 2020 - 09:38:21 EST


This adds an option '--inherit' to allow us trace children
processes spawned by our target.

Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>

---
v2: option name '--trace-children' -> '--inherit'.
---
tools/perf/Documentation/perf-ftrace.txt | 3 ++
tools/perf/builtin-ftrace.c | 38 ++++++++++++++++++++++++
2 files changed, 41 insertions(+)

diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index a18d640e90bb..66876e79cc24 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -64,6 +64,9 @@ OPTIONS
--buffer-size::
Set the size of per-cpu tracing buffer in KB.

+--inherit::
+ Trace children processes spawned by our target.
+
-T::
--trace-funcs=::
Only trace functions given by the argument. Multiple functions
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 686d744d5025..b2651b9bd6d0 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -40,6 +40,7 @@ struct perf_ftrace {
int graph_depth;
unsigned initial_delay;
unsigned buffer_size_kb;
+ bool inherit;
};

struct filter_entry {
@@ -178,9 +179,27 @@ static int write_tracing_file_int(const char *name, int value)
return 0;
}

+static int write_tracing_option_file(const char *name, const char *val)
+{
+ char *file;
+ int ret;
+
+ if (asprintf(&file, "options/%s", name) < 0)
+ return -1;
+
+ ret = __write_tracing_file(file, val, false);
+ free(file);
+ return ret;
+}
+
static int reset_tracing_cpu(void);
static void reset_tracing_filters(void);

+static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
+{
+ write_tracing_option_file("function-fork", "0");
+}
+
static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
{
if (write_tracing_file("tracing_on", "0") < 0)
@@ -199,6 +218,7 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
return -1;

reset_tracing_filters();
+ reset_tracing_options(ftrace);
return 0;
}

@@ -336,6 +356,17 @@ static int set_tracing_buffer_size_kb(struct perf_ftrace *ftrace)
return 0;
}

+static int set_tracing_trace_inherit(struct perf_ftrace *ftrace)
+{
+ if (!ftrace->inherit)
+ return 0;
+
+ if (write_tracing_option_file("function-fork", "1") < 0)
+ return -1;
+
+ return 0;
+}
+
static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
{
char *trace_file;
@@ -405,6 +436,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
goto out_reset;
}

+ if (set_tracing_trace_inherit(ftrace) < 0) {
+ pr_err("failed to set tracing option function-fork\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;
@@ -580,6 +616,8 @@ int cmd_ftrace(int argc, const char **argv)
"ms to wait before starting tracing after program start"),
OPT_UINTEGER('m', "buffer-size", &ftrace.buffer_size_kb,
"size of per cpu buffer in kb"),
+ OPT_BOOLEAN(0, "inherit", &ftrace.inherit,
+ "trace children processes"),
OPT_END()
};

--
2.25.1