[PATCH] trace-cmd: Add record --clock option to specify a trace clock

[Ian Webster <ian@planetaryresources.com>]

This change adds a --clock option to trace-cmd record. It simply writes
trace_clock on debugfs. Examples of valid choices on most systems are: local,
global, counter, and any other choice compatible with ftrace.

This complements Yoshihiro Yunomae's change 8c9867c (trace-cmd: Add support for
extracting trace_clock in report).

Signed-off-by: Ian Webster <ian@planetaryresources.com>
---
Documentation/trace-cmd-record.1.txt |    5 +++++
trace-record.c                       |   19 +++++++++++++++++++
trace-usage.c                        |    1 +
3 files changed, 25 insertions(+)

diff --git a/Documentation/trace-cmd-record.1.txt b/Documentation/trace-cmd-record.1.txt
index 832a257..201be2b 100644
--- a/Documentation/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd-record.1.txt
@@ -240,6 +240,11 @@ OPTIONS
     timestamp to gettimeofday which will allow wall time output from the
     timestamps reading the created 'trace.dat' file.

+*--clock* 'clock_name'::
+    When an event is recorded into the ring buffer, a timestamp is added. This
+    stamp comes from the specified clock. Ftrace uses the "local" clock by
+    default. Other common clocks include: global, counter, uptime, perf, x86-tsc.
+
EXAMPLES
--------

diff --git a/trace-record.c b/trace-record.c
index 0199627..18de026 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -399,6 +399,20 @@ static int set_ftrace(int set, int use_proc)
  return 0;
}

+static void set_trace_clock(char *clock_choice)
+{
+ FILE *fp;
+ char *path;
+
+ path = tracecmd_get_tracing_file("trace_clock");
+ fp = fopen(path, "w");
+ if (!fp)
+   die("writing to '%s'", path);
+ tracecmd_put_tracing_file(path);
+ fwrite(clock_choice, 1, strlen(clock_choice), fp);
+ fclose(fp);
+}
+
static char *
get_instance_file(struct buffer_instance *instance, const char *file)
{
@@ -2279,6 +2293,7 @@ static void record_all_events(void)
}

enum {
+ OPT_clock = 252,
  OPT_nosplice  = 253,
  OPT_funcstack = 254,
  OPT_date  = 255,
@@ -2351,6 +2366,7 @@ void trace_record (int argc, char **argv)
      {"func-stack", no_argument, NULL, OPT_funcstack},
      {"nosplice", no_argument, NULL, OPT_nosplice},
      {"help", no_argument, NULL, '?'},
+     {"clock", required_argument, NULL, OPT_clock},
      {NULL, 0, NULL, 0}
    };

@@ -2530,6 +2546,9 @@ void trace_record (int argc, char **argv)
    case OPT_nosplice:
      recorder_flags |= TRACECMD_RECORD_NOSPLICE;
      break;
+   case OPT_clock:
+     set_trace_clock(optarg);
+     break;
    default:
      usage(argv);
    }
diff --git a/trace-usage.c b/trace-usage.c
index b8f26e6..54dbb85 100644
--- a/trace-usage.c
+++ b/trace-usage.c
@@ -46,6 +46,7 @@ static struct usage_help usage_help[] = {
    "          -i do not fail if an event is not found\n"
    "          --func-stack perform a stack trace for function tracer\n"
    "             (use with caution)\n"
+   "          --clock change the method used to produce trace timestamps\n"
  },
  {
    "start",
--
1.7.9.5