anolis: sched: Credit clarification for BVT and its related work

ANBZ: torvalds#781

Group Identity is a totally different feature from BVT, and the
defination and logic of bvt_warp_ns has been totally reformed.

While 10 lines of code are related to BVT paper and it's code
(Jacob Leverich), this patch gives credit to BVT and its related
work.

Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Acked-by: Michael Wang <yun.wang@linux.alibaba.com>

kernel/sched/core.c

@@ -7087,7 +7087,30 @@ static struct cftype cpu_legacy_files[] = {
 	},
 #endif
 #ifdef CONFIG_GROUP_IDENTITY
-	/* legacy bvt interface */
+	/* legacy bvt interface
+	 *
+	 * BVT(Borrowed Virtual Time) is derived from paper:
+	 * "Borrowed-virtual-time (BVT) scheduling: supporting
+	 * latency-sensitive threads in a general-purpose scheduler"
+	 * Link: https://dl.acm.org/doi/abs/10.1145/319344.319169
+	 *
+	 * Jacob Leverich implemented the idea of this paper, and
+	 * 'bvt_warp_ns' interface is derived from Leverich's code.
+	 * Link: https://gist.github.com/leverich/5913713.
+	 *
+	 * Now we have reformed the whole idea, and only reserved
+	 * the name of 'bvt_warp_ns' to be compalitible.
+	 *
+	 * 'bvt_warp_ns' will be converted into identity when written.
+	 * The correspondence of bvt_warp_ns and identity follows:
+	 * bvt	identity value	identity
+	 * -2	9		ID_UNDERCLASS | ID_IDLE_SAVER
+	 * -1	9		ID_UNDERCLASS | ID_IDLE_SAVER
+	 * 0	0		ID_NORMAL
+	 * 1	18		ID_HIGHCLASS | ID_IDLE_SEEKER
+	 * 2	22		ID_HIGHCLASS | ID_IDLE_SEEKER | ID_SMT_EXPELLER
+	 *
+	 */
 	{
 		.name = "bvt_warp_ns",
 		.read_s64 = cpu_bvt_warp_ns_read_s64,

kernel/sched/fair.c

@@ -112,6 +112,10 @@ unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
 
 #ifdef CONFIG_GROUP_IDENTITY
 /*
+ * Variable 'sysctl_sched_bvt_place_epsilon' is derived from
+ * https://gist.github.com/leverich/5913713.
+ * Author: Jacob Leverich
+ *
  * Waking batch tasks are placed sched_bvt_place_epsilon
  * nanoseconds relative to min_vruntime.
  *
@@ -5290,6 +5294,10 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 
 #ifdef CONFIG_GROUP_ENTITY
 	/*
+	 * The logic of punishing underclass is derived from
+	 * https://gist.github.com/leverich/5913713.
+	 * Author: Jacob Leverich
+	 *
 	 * The runtime penalty for underclass wakee to make sure
 	 * they won't interrupt other's execution too much.
 	 */

kernel/sysctl.c

@@ -519,6 +519,11 @@ static struct ctl_table kern_table[] = {
 #endif
 #ifdef CONFIG_GROUP_IDENTITY
 	{
+		/*
+		 * Variable 'sysctl_sched_bvt_place_epsilon' is derived from
+		 * https://gist.github.com/leverich/5913713.
+		 * Author: Jacob Leverich
+		 */
 		.procname	= "sched_bvt_place_epsilon",
 		.data		= &sysctl_sched_bvt_place_epsilon,
 		.maxlen		= sizeof(unsigned int),