linux-kernel - [PATCH 12/19] perf ftrace: add support for tracing children processes

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Date:   Sun, 10 May 2020 23:06:21 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Changbin Du <changbin.du@...il.com>
Subject: [PATCH 12/19] perf ftrace: add support for tracing children processes

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

Signed-off-by: Changbin Du <changbin.du@...il.com>
---
 tools/perf/builtin-ftrace.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index ab76ba66bd9e..8fd95c109fe8 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -46,6 +46,7 @@ struct perf_ftrace {
 	bool			funcgraph_tail;
 	bool			long_info;
 	unsigned		tracing_thresh;
+	bool			trace_children;
 };
 
 struct filter_entry {
@@ -200,6 +201,7 @@ static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
 	write_tracing_option_file("irq-info", "0");
 	write_tracing_option_file("userstacktrace", "0");
 	write_tracing_option_file("sym-userobj", "0");
+	write_tracing_option_file("function-fork", "0");
 }
 
 static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
@@ -441,6 +443,17 @@ static int set_tracing_funcgraph_tail(struct perf_ftrace *ftrace)
 	return 0;
 }
 
+static int set_tracing_trace_children(struct perf_ftrace *ftrace)
+{
+	if (!ftrace->trace_children)
+		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;
@@ -539,6 +552,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_reset;
 	}
 
+	if (set_tracing_trace_children(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;
@@ -686,6 +704,8 @@ int cmd_ftrace(int argc, const char **argv)
 		    "Show process names, PIDs, timestamps, irq-info if available"),
 	OPT_UINTEGER(0, "tracing-thresh", &ftrace.tracing_thresh,
 		     "Only show functions of which the duration is greater than <n>µs"),
+	OPT_BOOLEAN(0, "trace-children", &ftrace.trace_children,
+		    "Trace children processes"),
 	OPT_END()
 	};
 
-- 
2.25.1