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Subject[PATCH v4 07/17] perf ftrace: add option '--inherit' to trace children processes
Date
This adds an option '--inherit' to allow us trace children
processes spawned by our target.

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

---
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 98fe01d354d1..fd632bd9b2c1 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -61,6 +61,9 @@ OPTIONS
Set the size of per-cpu tracing buffer, <size> is expected to
be a number with appended unit character - B/K/M/G.

+--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 887e78b23a82..4efaa7b6a906 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -39,6 +39,7 @@ struct perf_ftrace {
struct list_head nograph_funcs;
int graph_depth;
unsigned long percpu_buffer_size;
+ bool inherit;
};

struct filter_entry {
@@ -177,9 +178,27 @@ 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)
@@ -198,6 +217,7 @@ 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_percpu_buffer_size(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;
@@ -599,6 +635,8 @@ int cmd_ftrace(int argc, const char **argv)
"Max depth for function graph tracer"),
OPT_CALLBACK('m', "buffer-size", &ftrace.percpu_buffer_size, "size",
"size of per cpu buffer", parse_buffer_size),
+ OPT_BOOLEAN(0, "inherit", &ftrace.inherit,
+ "trace children processes"),
OPT_END()
};

--
2.25.1
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