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Subject[PATCH v2 04/15] perf ftrace: add option -d/--delay to delay tracing
Date
This adds an option '-d/--delay' to allow us to start tracing some
times later after workload is launched.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
tools/perf/Documentation/perf-ftrace.txt | 4 ++++
tools/perf/builtin-ftrace.c | 19 ++++++++++++++++---
2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index e204bf6d50d8..fd1776deebd7 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -42,6 +42,10 @@ OPTIONS
--tid=::
Trace on existing thread id (comma separated list).

+-d::
+--delay::
+ Time (ms) to wait before starting tracing after program start.
+
-a::
--all-cpus::
Force system-wide collection. Scripts run without a <command>
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index b427ab3977ad..dceae70c3a22 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -38,6 +38,7 @@ struct perf_ftrace {
struct list_head graph_funcs;
struct list_head nograph_funcs;
int graph_depth;
+ unsigned initial_delay;
};

struct filter_entry {
@@ -402,13 +403,23 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
fcntl(trace_fd, F_SETFL, O_NONBLOCK);
pollfd.fd = trace_fd;

- if (write_tracing_file("tracing_on", "1") < 0) {
- pr_err("can't enable tracing\n");
- goto out_close_fd;
+ if (!ftrace->initial_delay) {
+ if (write_tracing_file("tracing_on", "1") < 0) {
+ pr_err("can't enable tracing\n");
+ goto out_close_fd;
+ }
}

perf_evlist__start_workload(ftrace->evlist);

+ if (ftrace->initial_delay) {
+ usleep(ftrace->initial_delay * 1000);
+ if (write_tracing_file("tracing_on", "1") < 0) {
+ pr_err("can't enable tracing\n");
+ goto out_close_fd;
+ }
+ }
+
while (!done) {
if (poll(&pollfd, 1, -1) < 0)
break;
@@ -535,6 +546,8 @@ int cmd_ftrace(int argc, const char **argv)
"Set nograph filter on given functions", parse_filter_func),
OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
"Max depth for function graph tracer"),
+ OPT_UINTEGER('d', "delay", &ftrace.initial_delay,
+ "ms to wait before starting tracing after program start"),
OPT_END()
};

--
2.25.1
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