sched: Add annotations to RT_GROUP_SCHED fields

Update comments to ease RT throttling understanding.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250310170442.504716-10-mkoutny@suse.com

Author: Werkov

kernel/sched/sched.h

@@ -813,17 +813,17 @@ struct rt_rq {
 
 #ifdef CONFIG_RT_GROUP_SCHED
 	int			rt_throttled;
-	u64			rt_time;
-	u64			rt_runtime;
+	u64			rt_time; /* consumed RT time, goes up in update_curr_rt */
+	u64			rt_runtime; /* allotted RT time, "slice" from rt_bandwidth, RT sharing/balancing */
 	/* Nests inside the rq lock: */
 	raw_spinlock_t		rt_runtime_lock;
 
 	unsigned int		rt_nr_boosted;
 
-	struct rq		*rq;
+	struct rq		*rq; /* this is always top-level rq, cache? */
 #endif
 #ifdef CONFIG_CGROUP_SCHED
-	struct task_group	*tg;
+	struct task_group	*tg; /* this tg has "this" rt_rq on given CPU for runnable entities */
 #endif
 };