perf: add perf-inject builtin

Currently, perf 'live mode' writes build-ids at the end of the
session, which isn't actually useful for processing live mode events.

What would be better would be to have the build-ids sent before any of
the samples that reference them, which can be done by processing the
event stream and retrieving the build-ids on the first hit.  Doing
that in perf-record itself, however, is off-limits.

This patch introduces perf-inject, which does the same job while
leaving perf-record untouched.  Normal mode perf still records the
build-ids at the end of the session as it should, but for live mode,
perf-inject can be injected in between the record and report steps
e.g.:

perf record -o - ./hackbench 10 | perf inject -v -b | perf report -v -i -

perf-inject reads a perf-record event stream and repipes it to stdout.
At any point the processing code can inject other events into the
event stream - in this case build-ids (-b option) are read and
injected as needed into the event stream.

Build-ids are just the first user of perf-inject - potentially
anything that needs userspace processing to augment the trace stream
with additional information could make use of this facility.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1272696080-16435-3-git-send-email-tzanussi@gmail.com>
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/tools/perf/util/trace-event-read.c b/tools/perf/util/trace-event-read.c
index 44889c9b5630..43f19c1fed3a 100644
--- a/tools/perf/util/trace-event-read.c
+++ b/tools/perf/util/trace-event-read.c
@@ -51,6 +51,7 @@ static int long_size;
 static unsigned long	page_size;
 
 static ssize_t calc_data_size;
+static bool repipe;
 
 static int do_read(int fd, void *buf, int size)
 {
@@ -62,6 +63,13 @@ static int do_read(int fd, void *buf, int size)
 		if (ret <= 0)
 			return -1;
 
+		if (repipe) {
+			int retw = write(STDOUT_FILENO, buf, ret);
+
+			if (retw <= 0 || retw != ret)
+				die("repiping input file");
+		}
+
 		size -= ret;
 		buf += ret;
 	}
@@ -116,6 +124,13 @@ static char *read_string(void)
 		if (!r)
 			die("no data");
 
+		if (repipe) {
+			int retw = write(STDOUT_FILENO, &c, 1);
+
+			if (retw <= 0 || retw != r)
+				die("repiping input file string");
+		}
+
 		buf[size++] = c;
 
 		if (!c)
@@ -454,7 +469,7 @@ struct record *trace_read_data(int cpu)
 	return data;
 }
 
-ssize_t trace_report(int fd)
+ssize_t trace_report(int fd, bool __repipe)
 {
 	char buf[BUFSIZ];
 	char test[] = { 23, 8, 68 };
@@ -465,6 +480,7 @@ ssize_t trace_report(int fd)
 	ssize_t size;
 
 	calc_data_size = 1;
+	repipe = __repipe;
 
 	input_fd = fd;
 
@@ -499,6 +515,7 @@ ssize_t trace_report(int fd)
 
 	size = calc_data_size - 1;
 	calc_data_size = 0;
+	repipe = false;
 
 	if (show_funcs) {
 		print_funcs();