perf counters: add support for group counters

Impact: add group counters

This patch adds the "counter groups" abstraction.

Groups of counters behave much like normal 'single' counters, with a
few semantic and behavioral extensions on top of that.

A counter group is created by creating a new counter with the open()
syscall's group-leader group_fd file descriptor parameter pointing
to another, already existing counter.

Groups of counters are scheduled in and out in one atomic group, and
they are also roundrobin-scheduled atomically.

Counters that are member of a group can also record events with an
(atomic) extended timestamp that extends to all members of the group,
if the record type is set to PERF_RECORD_GROUP.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index a2b4852e2d70..7af7d8965460 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -117,7 +117,10 @@ struct perf_data {
  * struct perf_counter - performance counter kernel representation:
  */
 struct perf_counter {
-	struct list_head		list;
+	struct list_head		list_entry;
+	struct list_head		sibling_list;
+	struct perf_counter		*group_leader;
+
 	int				active;
 #if BITS_PER_LONG == 64
 	atomic64_t			count;
@@ -158,7 +161,8 @@ struct perf_counter_context {
 	 * Protect the list of counters:
 	 */
 	spinlock_t		lock;
-	struct list_head	counters;
+
+	struct list_head	counter_list;
 	int			nr_counters;
 	int			nr_active;
 	struct task_struct	*task;