[PATCH] perf script: introduce deltatime option

[Hagen Paul Pfeifer]

For some kind of analysis a deltatime output is more human friendly and reduce
the cognitive load for further analysis.

The following output demonstrate the new option "deltatime": calculate
the time difference in relation to the previous event.

$ perf script --deltatime
test  2525 [001]     0.000000:            sdt_libev:ev_add: (5635e72a5ebd)
test  2525 [001]     0.000091:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     1.000051: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1
test  2525 [001]     0.000685:            sdt_libev:ev_add: (5635e72a5ebd)
test  2525 [001]     0.000048:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     1.000104: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1
test  2525 [001]     0.003895:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     0.996034: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1
test  2525 [001]     0.000058:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     1.000004: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1
test  2525 [001]     0.000064:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     0.999934: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1
test  2525 [001]     0.000056:  sdt_libev:epoll_wait_enter: (5635e72a76a9)
test  2525 [001]     0.999930: sdt_libev:epoll_wait_return: (5635e72a772e) arg1=1

Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Hagen Paul Pfeifer <hagen@xxxxxxxx>
---
 tools/perf/builtin-script.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index e2406b291c1c..d5566b121159 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -63,7 +63,9 @@
 static char const		*script_name;
 static char const		*generate_script_lang;
 static bool			reltime;
+static bool			deltatime;
 static u64			initial_time;
+static u64			previous_time;
 static bool			debug_mode;
 static u64			last_timestamp;
 static u64			nr_unordered;
@@ -704,6 +706,13 @@ static int perf_sample__fprintf_start(struct perf_sample *sample,
 			if (!initial_time)
 				initial_time = sample->time;
 			t = sample->time - initial_time;
+		} else if (deltatime) {
+			if (previous_time)
+				t = sample->time - previous_time;
+			else {
+				t = 0;
+			}
+			previous_time = sample->time;
 		}
 		nsecs = t;
 		secs = nsecs / NSEC_PER_SEC;
@@ -3551,6 +3560,7 @@ int cmd_script(int argc, const char **argv)
 		     "anything beyond the specified depth will be ignored. "
 		     "Default: kernel.perf_event_max_stack or " __stringify(PERF_MAX_STACK_DEPTH)),
 	OPT_BOOLEAN(0, "reltime", &reltime, "Show time stamps relative to start"),
+	OPT_BOOLEAN(0, "deltatime", &deltatime, "Show time stamps relative to previous event"),
 	OPT_BOOLEAN('I', "show-info", &show_full_info,
 		    "display extended information from perf.data file"),
 	OPT_BOOLEAN('\0', "show-kernel-path", &symbol_conf.show_kernel_path,
@@ -3647,6 +3657,13 @@ int cmd_script(int argc, const char **argv)
 		}
 	}
 
+	if (reltime && deltatime) {
+		fprintf(stderr,
+			"reltime and deltatime - the two don't get along well. "
+			"Please limit to --reltime or --deltatime.\n");
+		return -1;
+	}
+
 	if (itrace_synth_opts.callchain &&
 	    itrace_synth_opts.callchain_sz > scripting_max_stack)
 		scripting_max_stack = itrace_synth_opts.callchain_sz;
-- 
2.24.1