trace-cmd record: Add --ts-offset for timestamp of events

Add an option to allow users to add a timestamp offset to all events. This
is useful when wanting to merge the resulting trace.dat file with another
trace.dat file where the timestamps are shifted by a given offset.
Specifically for virtual machines, where the host and guest have a known
offset, and the recording of the host (or guest) can use this option to
remove the need to add it when merging the trace.dat files together.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 52 insertions, 6 deletions

diff --git a/Documentation/trace-cmd-record.1.txt b/Documentation/trace-cmd-record.1.txt
index 2a368fed..d88050d8 100644
--- a/Documentation/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd-record.1.txt
@@ -286,6 +286,14 @@ OPTIONS
 
     See trace-cmd-profile(1) for format.
 
+*--ts-offset offset*::
+    Add an offset for the timestamp in the trace.dat file. This will add a
+    offset option into the trace.dat file such that a trace-cmd report will
+    offset all the timestamps of the events by the given offset. The offset
+    is in raw units. That is, if the event timestamps are in nanoseconds
+    the offset will also be in nanoseconds even if the displayed units are
+    in microseconds.
+
 *--stderr*::
     Have output go to stderr instead of stdout, but the output of the command
     executed will not be changed. This is useful if you want to monitor the
diff --git a/trace-cmd.h b/trace-cmd.h
index ad3a5051..526ced28 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -89,6 +89,7 @@ enum {
 	TRACECMD_OPTION_TRACECLOCK,
 	TRACECMD_OPTION_UNAME,
 	TRACECMD_OPTION_HOOK,
+	TRACECMD_OPTION_OFFSET,
 };
 
 enum {
diff --git a/trace-input.c b/trace-input.c
index 07b5aab0..5e646420 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -1980,7 +1980,17 @@ static int handle_options(struct tracecmd_input *handle)
 			offset = strtoll(buf, NULL, 0);
 			/* Convert from micro to nano */
 			offset *= 1000;
-			handle->ts_offset = offset;
+			handle->ts_offset += offset;
+			break;
+		case TRACECMD_OPTION_OFFSET:
+			/*
+			 * Similar to date option, but just adds an
+			 * offset to the timestamp.
+			 */
+			if (handle->flags & TRACECMD_FL_IGNORE_DATE)
+				break;
+			offset = strtoll(buf, NULL, 0);
+			handle->ts_offset += offset;
 			break;
 		case TRACECMD_OPTION_CPUSTAT:
 			buf[size-1] = '\n';
diff --git a/trace-record.c b/trace-record.c
index 84e311fb..ea47848a 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -2862,7 +2862,13 @@ static void print_stat(struct buffer_instance *instance)
 		trace_seq_do_printf(&instance->s_print[cpu]);
 }
 
-static void record_data(char *date2ts)
+enum {
+	DATA_FL_NONE		= 0,
+	DATA_FL_DATE		= 1,
+	DATA_FL_OFFSET		= 2,
+};
+
+static void record_data(char *date2ts, int flags)
 {
 	struct tracecmd_option **buffer_options;
 	struct tracecmd_output *handle;
@@ -2901,9 +2907,18 @@ static void record_data(char *date2ts)
 		if (!handle)
 			die("Error creating output file");
 
-		if (date2ts)
-			tracecmd_add_option(handle, TRACECMD_OPTION_DATE,
-					    strlen(date2ts)+1, date2ts);
+		if (date2ts) {
+			int type = 0;
+
+			if (flags & DATA_FL_DATE)
+				type = TRACECMD_OPTION_DATE;
+			else if (flags & DATA_FL_OFFSET)
+				type = TRACECMD_OPTION_OFFSET;
+
+			if (type)
+				tracecmd_add_option(handle, type,
+						    strlen(date2ts)+1, date2ts);
+		}
 
 		/* Only record the top instance under TRACECMD_OPTION_CPUSTAT*/
 		if (!no_top_instance()) {
@@ -3995,6 +4010,7 @@ void update_first_instance(struct buffer_instance *instance, int topt)
 }
 
 enum {
+	OPT_tsoffset	= 249,
 	OPT_bycomm	= 250,
 	OPT_stderr	= 251,
 	OPT_profile	= 252,
@@ -4032,6 +4048,7 @@ void trace_record (int argc, char **argv)
 	int manual = 0;
 	int topt = 0;
 	int do_child = 0;
+	int data_flags = 0;
 
 	int c;
 
@@ -4198,6 +4215,7 @@ void trace_record (int argc, char **argv)
 			{"profile", no_argument, NULL, OPT_profile},
 			{"stderr", no_argument, NULL, OPT_stderr},
 			{"by-comm", no_argument, NULL, OPT_bycomm},
+			{"ts-offset", required_argument, NULL, OPT_tsoffset},
 			{"help", no_argument, NULL, '?'},
 			{NULL, 0, NULL, 0}
 		};
@@ -4429,6 +4447,9 @@ void trace_record (int argc, char **argv)
 			break;
 		case OPT_date:
 			date = 1;
+			if (data_flags & DATA_FL_OFFSET)
+				die("Can not use both --date and --ts-offset");
+			data_flags |= DATA_FL_DATE;
 			break;
 		case OPT_funcstack:
 			func_stack = 1;
@@ -4451,6 +4472,12 @@ void trace_record (int argc, char **argv)
 		case OPT_bycomm:
 			trace_profile_set_merge_like_comms();
 			break;
+		case OPT_tsoffset:
+			date2ts = strdup(optarg);
+			if (data_flags & DATA_FL_DATE)
+				die("Can not use both --date and --ts-offset");
+			data_flags |= DATA_FL_OFFSET;
+			break;
 		default:
 			usage(argv);
 		}
@@ -4614,7 +4641,7 @@ void trace_record (int argc, char **argv)
 	}
 
 	if (record || extract) {
-		record_data(date2ts);
+		record_data(date2ts, data_flags);
 		delete_thread_data();
 	} else
 		print_stats();