sched: Introduce temporary FAIR_GROUP_SCHED dependency for load-tracking

While per-entity load-tracking is generally useful, beyond computing shares
distribution, e.g. runnable based load-balance (in progress), governors,
power-management, etc.

These facilities are not yet consumers of this data.  This may be trivially
reverted when the information is required; but avoid paying the overhead for
calculations we will not use until then.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.422162369@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e483ccb08ce6..e1581a029e3d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1168,7 +1168,13 @@ struct sched_entity {
         /* rq "owned" by this entity/group: */
         struct cfs_rq           *my_q;
 #endif
-#ifdef CONFIG_SMP
+/*
+ * Load-tracking only depends on SMP, FAIR_GROUP_SCHED dependency below may be
+ * removed when useful for applications beyond shares distribution (e.g.
+ * load-balance).
+ */
+#if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)
+        /* Per-entity load-tracking */
         struct sched_avg        avg;
 #endif
 };