Initial work to #6

    `YIELD_MARK` only applies if `cfs_rq->h_nr_running > 1`
    `YIELD_UNMARK` on migrate_task

patches/5.15/tt-5.15-r2.patch

@@ -134,10 +134,10 @@ index 978fcfca5871..464b134de739 100644
  obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o
 diff --git a/kernel/sched/bs.c b/kernel/sched/bs.c
 new file mode 100644
-index 000000000000..758cd410d6e6
+index 000000000000..bbeb0c844325
 --- /dev/null
 +++ b/kernel/sched/bs.c
-@@ -0,0 +1,1181 @@
+@@ -0,0 +1,1179 @@
 +// SPDX-License-Identifier: GPL-2.0
 +/*
 + * TT Scheduler Class (SCHED_NORMAL/SCHED_BATCH)
@@ -161,9 +161,6 @@ index 000000000000..758cd410d6e6
 +#define RACE_TIME 40000000
 +#define FACTOR (RACE_TIME / HZ_PERIOD)
 +
-+#define YIELD_MARK(ttn)		((ttn)->vruntime |= 0x8000000000000000ULL)
-+#define YIELD_UNMARK(ttn)	((ttn)->vruntime &= 0x7FFFFFFFFFFFFFFFULL)
-+
 +#define IS_REALTIME(ttn)	((ttn)->task_type == TT_REALTIME)
 +#define IS_INTERACTIVE(ttn)	((ttn)->task_type == TT_INTERACTIVE)
 +#define IS_NO_TYPE(ttn)		((ttn)->task_type == TT_NO_TYPE)
@@ -558,14 +555,15 @@ index 000000000000..758cd410d6e6
 +	struct task_struct *curr = rq->curr;
 +	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
 +
-+	YIELD_MARK(&curr->se.tt_node);
-+
 +	/*
 +	 * Are we the only task in the tree?
 +	 */
 +	if (unlikely(rq->nr_running == 1))
 +		return;
 +
++	if (cfs_rq->h_nr_running > 1)
++		YIELD_MARK(&curr->se.tt_node);
++
 +	if (curr->policy != SCHED_BATCH) {
 +		update_rq_clock(rq);
 +		/*
@@ -1321,10 +1319,12 @@ index 000000000000..758cd410d6e6
 +}
 diff --git a/kernel/sched/bs.h b/kernel/sched/bs.h
 new file mode 100644
-index 000000000000..d413aad1d0a3
+index 000000000000..721eb690abeb
 --- /dev/null
 +++ b/kernel/sched/bs.h
-@@ -0,0 +1,305 @@
+@@ -0,0 +1,306 @@
++#define YIELD_MARK(ttn)		((ttn)->vruntime |= 0x8000000000000000ULL)
++#define YIELD_UNMARK(ttn)	((ttn)->vruntime &= 0x7FFFFFFFFFFFFFFFULL)
 +
 +/*
 + * After fork, child runs first. If set to 0 (default) then
@@ -1371,13 +1371,12 @@ index 000000000000..d413aad1d0a3
 +		 */
 +		remove_entity_load_avg(&p->se);
 +	}
-+
-+	/* We have migrated, no longer consider this task hot */
-+	p->se.exec_start = 0;
 +#endif
 +	/* Tell new CPU we are migrated */
 +	p->se.avg.last_update_time = 0;
 +
++	YIELD_UNMARK(&p->se.tt_node);
++
 +	update_scan_period(p, new_cpu);
 +}
 +