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;