perf tools: Add an option to multiplex counters in a single channel

Add an option to multiplex counters output in the channel of
the group leader, ie: the first counter opened:

	-M --multiplex

The effect is better serialized samples. This is especially
useful for tracepoint samples that need to be well serialized
for their post-processing.

Also make use of this option in 'perf sched'.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 8 insertions, 0 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 99a12fe86e9f..79f99dba5be0 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -48,6 +48,7 @@ static int			call_graph			= 0;
 static int                      inherit_stat                    = 0;
 static int                      no_samples                      = 0;
 static int                      sample_address                  = 0;
+static int                      multiplex                       = 0;
 
 static long                     samples;
 static struct timeval           last_read;
@@ -485,6 +486,9 @@ try_again:
                 exit(-1);
         }
 
+        if (multiplex && fd[nr_cpu][counter] != group_fd)
+                ioctl(fd[nr_cpu][counter], PERF_COUNTER_IOC_SET_OUTPUT, group_fd);
+
         ioctl(fd[nr_cpu][counter], PERF_COUNTER_IOC_ENABLE);
 }
 
@@ -681,6 +685,8 @@ static const struct option options[] = {
                     "Sample addresses"),
         OPT_BOOLEAN('n', "no-samples", &no_samples,
                     "don't sample"),
+        OPT_BOOLEAN('M', "multiplex", &multiplex,
+                    "multiplex counter output in a single channel"),
         OPT_END()
 };
 
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 8db0fd222f80..686af633b35b 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -1660,6 +1660,8 @@ static const char *record_args[] = {
         "record",
         "-a",
         "-R",
+        "-M",
+        "-g",
         "-c", "1",
         "-e", "sched:sched_switch:r",
         "-e", "sched:sched_stat_wait:r",