Linux 核心設計: Scheduler(5): EEVDF Scheduler/1

gantt
    title time
    dateFormat DD
		axisFormat %d
        section process A
            tA_1 : 01, 1d
            tA_2 : 04, 1d
            tA_3 : 05, 1d
            tA_4 : 08, 1d
        section process B
            tB_1 : crit, 02, 2d
            tB_2 : crit, 06, 2d

/* join competition */
void join(client_struct *client)
{
    /* update total weight of al l active clients */
    TotalWeight += client->weight;
    /* update virtual time according to client lag */
    VirtualTime = get_current_vt() - client->lag/TotalWeight;
    /* issue request */
    client->req->ve = VirtualTime;
    client->req->vd = req->ve + QuantumSize/client->weight;
    insert_req(client->req);
}

/* leave competition */
void leave(client_struct *client)
{
    /* update total weight of all active clients */
    TotalWeight -= client->weight;
    /* update virtual time according to client lag */
    VirtualTime = get_current_vt() + client->lag/TotalWeight;
    /* delete request */
    delete_req(client->req);
}

/* change client weight */
void change_weight(client_struct *client, int new_weight)
{
    /* partial update virtual time according to client lag */
    VirtualTime = get_current_vt() + client->lag/(TotalWeight - client->weight);
    /* update total weight of all active clients */
    TotalWeight += new_weight - client->weight;
    /* update client's weight */
    client->weight = new_weight;
    /* update virtual time */
    VirtualTime -= client->lag/TotalWeight;
}

/* dispatch function */
void EEVDF_dispatch()
{
    int used;
    /* get eligible request with earliest virtual deadline */
    req = get_req(ReqTree, get_curreent_vt());
    /* allocate resource to client with earliest eligible virtual dead line */
    used = allocate(req->client);
    /* update client's lag */
    update_lag(client, used);
    /* current request has been fullfiled; delete it */
    delete_req(ReqTree, req);
    /* issue new request */
    client->req->ve += used/client->weight;
    client->req->vd = client->req->ve + QuantumSize/client->weight;
    insert_req(client->req);
}

/* get eligible request with earliest dead line */
req_struct *get_req(req_struct *root, time_v vtime)
{
    req_struct *node = root, *st_tree = NULL, *path_req = NULL;
    while (node) {
        if (node->ve <= vtime) {
            /* update node with earliest dead line along path. */
            if ((!path_req) || (path_req->vd > node->vd))
                path_req = node;
            /* update root of subtree containing earliest dead line */
            if ((!st_tree) || (node->left && st_tree->min_vd > node->left->min_vd))
                st_tree = node->left;
            node = node->right;
        } else
            node = node->left;
    }
    
    /* check whether node with earliest dead line was along path */
    if ((!st_tree) || (st_tree->min_vd >= path_req->vd))
        return path_req;
    /* return node with earliest dead line from subtree */
    for (node = st_tree; node; ) {
        /* if node found, return it */
        if (st_tree->min_vd == node->vd)
            return node;
        if (node->min_vd == node->left->min_vd)
            node = node->left;
        else
            node = node->right;
    }
}

/* insert new request */
void insert_req(req_struct *root, req_str *req)
{
    req_struct *node = root;
    while (node) {
        /* update min vd of current node */
        if (node->min_vd > req->vd)
            node->min_vd = req->vd;
        if (node->ve < req->ve) {
            if (!node->right) {
                /* insert new request as right child */
                node->right = req;
                req->parent = node;
                return;
            }
           node = node->right;
        } else {
            if (!node->left) {
                /* insert new request as left child */
                node->left = req;
                req->parent = node;
                return;
            }
                node = node->left;
        }
    }
}

/* update min_vd fields of all ancestors of node */
void backward_update(req_struct *node, req_struct *root)
{
    do {
        node->min_vd = node->vd;
        /* check for right child */
        if (node->right && node->min_vd > node->right->min_vd)
            node->min_vd = node->right->min_vd;
        /* check for left child */
        if (node->left && node->min_vd > node->left->min_vd)
            node->min_vd = node->left->min_vd;
    } while ((node != root) && (node = node->parent))
}

/* delete specified request */
req_struct *delete_req(req_struct *root, req_struct *req)
{
    req_struct *child, *succ;
    if (!req->right || !req->left) { /* cases (i) and (ii) */
        /* get node's child, if any */
        child = get_child(req);
        /* remove node form tree */
        if (child)
            child->parent = node->parent;
        if (req == root)
            return child;
        if (req->parent->left == req)
            req->parent->left = child;
        else
            req->parent->right = child;
        /* update min vd of node's ancestors */
        backward_update(parent, root);
    } else { /* case (iii) */
        /* get node's successor */
        succ = get_succesor(req);
        /* delete node's successor from tree */
        req->right = delete_req(req->right, succ);
        /* swap node with its successor */
        swap_node(succ, req);
        /* update min vd of node's ancestors */
        backward_update(req, root);
    }
    return root;
}

@@ -554,6 +554,9 @@ struct cfs_rq {
 	unsigned int		idle_nr_running;   /* SCHED_IDLE */
 	unsigned int		idle_h_nr_running; /* SCHED_IDLE */
 
+	s64			avg_vruntime;
+	u64			avg_load;
+
 	u64			exec_clock;
 	u64			min_vruntime;

/*
 * Compute virtual time from the per-task service numbers:
 *
 * Fair schedulers conserve lag:
 *
+ *   \Sum lag_i = 0
 *
 * Where lag_i is given by:
 *
 *   lag_i = S - s_i = w_i * (V - v_i)
 *
 * Where S is the ideal service time and V is it's virtual time counterpart.
 */

 /* Therefore:
 *
 *   \Sum lag_i = 0
 *   \Sum w_i * (V - v_i) = 0
 *   \Sum w_i * V - w_i * v_i = 0
 *
 * From which we can solve an expression for V in v_i (which we have in
 * se->vruntime):
 *
 *       \Sum v_i * w_i   \Sum v_i * w_i
 *   V = -------------- = --------------
 *          \Sum w_i            W
 *
 * Specifically, this is the weighted average of all entity virtual runtimes.
 */

 /*
  * [[ NOTE: this is only equal to the ideal scheduler under the condition
  *          that join/leave operations happen at lag_i = 0, otherwise the
  *          virtual time has non-continguous motion equivalent to:
  *
  *	      V +-= lag_i / W
  *
  *	    Also see the comment in place_entity() that deals with this. ]]
  *
  * However, since v_i is u64, and the multiplcation could easily overflow
  * transform it into a relative form that uses smaller quantities:
  *
  * Substitute: v_i == (v_i - v0) + v0
  *
  *     \Sum ((v_i - v0) + v0) * w_i   \Sum (v_i - v0) * w_i
  * V = ---------------------------- = --------------------- + v0
  *                  W                            W
  *
  * Which we track using:
  *
  *                    v0 := cfs_rq->min_vruntime
  * \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime
  *              \Sum w_i := cfs_rq->avg_load
  *
  * Since min_vruntime is a monotonic increasing variable that closely tracks
  * the per-task service, these deltas: (v_i - v), will be in the order of the
  * maximal (virtual) lag induced in the system due to quantisation.
  *
  * Also, we use scale_load_down() to reduce the size.
  *
  * As measured, the max (key * weight) value was ~44 bits for a kernel build.
  */

static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	return (s64)(se->vruntime - cfs_rq->min_vruntime);
}

static void
avg_vruntime_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	unsigned long weight = scale_load_down(se->load.weight);
	s64 key = entity_key(cfs_rq, se);

	cfs_rq->avg_vruntime += key * weight;
	cfs_rq->avg_load += weight;
}

static void
avg_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	unsigned long weight = scale_load_down(se->load.weight);
	s64 key = entity_key(cfs_rq, se);

	cfs_rq->avg_vruntime -= key * weight;
	cfs_rq->avg_load -= weight;
}

static inline
void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta)
{
	/*
	 * v' = v + d ==> avg_vruntime' = avg_runtime - d*avg_load
	 */
	cfs_rq->avg_vruntime -= cfs_rq->avg_load * delta;
}

static u64 __update_min_vruntime(struct cfs_rq *cfs_rq, u64 vruntime)
{
	u64 min_vruntime = cfs_rq->min_vruntime;
	/*
	 * open coded max_vruntime() to allow updating avg_vruntime
	 */
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta > 0) {
		avg_vruntime_update(cfs_rq, delta);
		min_vruntime = vruntime;
	}
	return min_vruntime;
}

u64 avg_vruntime(struct cfs_rq *cfs_rq)
{
	struct sched_entity *curr = cfs_rq->curr;
	s64 avg = cfs_rq->avg_vruntime;
	long load = cfs_rq->avg_load;

	if (curr && curr->on_rq) {
		unsigned long weight = scale_load_down(curr->load.weight);

		avg += entity_key(cfs_rq, curr) * weight;
		load += weight;
	}

	if (load)
		avg = div_s64(avg, load);

	return cfs_rq->min_vruntime + avg;
}

@@ -642,12 +767,14 @@ static inline bool __entity_less(struct
  */
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
+	avg_vruntime_add(cfs_rq, se);
 	rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
+	avg_vruntime_sub(cfs_rq, se);
 }
 
 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
@@ -3379,6 +3506,8 @@ static void reweight_entity(struct cfs_r
 		/* commit outstanding execution time */
 		if (cfs_rq->curr == se)
 			update_curr(cfs_rq);
+		else
+			avg_vruntime_sub(cfs_rq, se);
 		update_load_sub(&cfs_rq->load, se->load.weight);
 	}
 	dequeue_load_avg(cfs_rq, se);
@@ -3394,9 +3523,11 @@ static void reweight_entity(struct cfs_r
 #endif
 
 	enqueue_load_avg(cfs_rq, se);
-	if (se->on_rq)
+	if (se->on_rq) {
 		update_load_add(&cfs_rq->load, se->load.weight);
-
+		if (cfs_rq->curr != se)
+			avg_vruntime_add(cfs_rq, se);
+	}
 }

@@ -626,10 +626,9 @@ static void print_rq(struct seq_file *m,
 
 void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 {
-	s64 MIN_vruntime = -1, min_vruntime, max_vruntime = -1,
-		spread, rq0_min_vruntime, spread0;
+	s64 left_vruntime = -1, min_vruntime, right_vruntime = -1, spread;
+	struct sched_entity *last, *first;
 	struct rq *rq = cpu_rq(cpu);
-	struct sched_entity *last;
 	unsigned long flags;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
@@ -643,26 +642,25 @@ void print_cfs_rq(struct seq_file *m, in
 			SPLIT_NS(cfs_rq->exec_clock));
 
 	raw_spin_rq_lock_irqsave(rq, flags);
-	if (rb_first_cached(&cfs_rq->tasks_timeline))
-		MIN_vruntime = (__pick_first_entity(cfs_rq))->vruntime;
+	first = __pick_first_entity(cfs_rq);
+	if (first)
+		left_vruntime = first->vruntime;
 	last = __pick_last_entity(cfs_rq);
 	if (last)
-		max_vruntime = last->vruntime;
+		right_vruntime = last->vruntime;
 	min_vruntime = cfs_rq->min_vruntime;
-	rq0_min_vruntime = cpu_rq(0)->cfs.min_vruntime;
 	raw_spin_rq_unlock_irqrestore(rq, flags);
-	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "MIN_vruntime",
-			SPLIT_NS(MIN_vruntime));
+
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "left_vruntime",
+			SPLIT_NS(left_vruntime));
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "min_vruntime",
 			SPLIT_NS(min_vruntime));
-	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "max_vruntime",
-			SPLIT_NS(max_vruntime));
-	spread = max_vruntime - MIN_vruntime;
-	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "spread",
-			SPLIT_NS(spread));
-	spread0 = min_vruntime - rq0_min_vruntime;
-	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "spread0",
-			SPLIT_NS(spread0));
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "avg_vruntime",
+			SPLIT_NS(avg_vruntime(cfs_rq)));
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "right_vruntime",
+			SPLIT_NS(right_vruntime));
+	spread = right_vruntime - left_vruntime;
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "spread", SPLIT_NS(spread));
 	SEQ_printf(m, "  .%-30s: %d\n", "nr_spread_over",
 			cfs_rq->nr_spread_over);
 	SEQ_printf(m, "  .%-30s: %d\n", "nr_running", cfs_rq->nr_running);

 /*
- * Place new tasks ahead so that they do not starve already running
- * tasks
- */
-SCHED_FEAT(START_DEBIT, true)
-
-/*

@@ -906,16 +906,6 @@ static u64 sched_slice(struct cfs_rq *cf
 	return slice;
 }
 
-/*
- * We calculate the vruntime slice of a to-be-inserted task.
- *
- * vs = s/w
- */
-static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-	return calc_delta_fair(sched_slice(cfs_rq, se), se);
-}
-
 #include "pelt.h"
 #ifdef CONFIG_SMP
 
@@ -4862,16 +4852,7 @@ static inline bool entity_is_long_sleepe
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
-	u64 vruntime = cfs_rq->min_vruntime;
-
-	/*
-	 * The 'current' period is already promised to the current tasks,
-	 * however the extra weight of the new task will slow them down a
-	 * little, place the new task so that it fits in the slot that
-	 * stays open at the end.
-	 */
-	if (initial && sched_feat(START_DEBIT))
-		vruntime += sched_vslice(cfs_rq, se);
+	u64 vruntime = avg_vruntime(cfs_rq);

@@ -555,8 +555,9 @@ struct sched_entity {
 
 	u64				exec_start;
 	u64				sum_exec_runtime;
-	u64				vruntime;
 	u64				prev_sum_exec_runtime;
+	u64				vruntime;
+	s64				vlag;
 
 	u64				nr_migrations;

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4463,6 +4463,7 @@ static void __sched_fork(unsigned long c
 	p->se.prev_sum_exec_runtime	= 0;
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
+	p->se.vlag			= 0;
 	INIT_LIST_HEAD(&p->se.group_node);

@@ -3492,6 +3501,8 @@ dequeue_load_avg(struct cfs_rq *cfs_rq,
 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 			    unsigned long weight)
 {
+	unsigned long old_weight = se->load.weight;
+
 	if (se->on_rq) {
 		/* commit outstanding execution time */
 		if (cfs_rq->curr == se)
@@ -3504,6 +3515,14 @@ static void reweight_entity(struct cfs_r
 
 	update_load_set(&se->load, weight);
 
+	if (!se->on_rq) {
+		/*
+		 * Because we keep se->vlag = V - v_i, while: lag_i = w_i*(V - v_i),
+		 * we need to scale se->vlag when w_i changes.
+		 */
+		se->vlag = div_s64(se->vlag * old_weight, weight);
+	}
+

/*
 * lag_i = S - s_i = w_i * (V - v_i)
 */
void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	SCHED_WARN_ON(!se->on_rq);
	se->vlag = avg_vruntime(cfs_rq) - se->vruntime;
}

@@ -5066,6 +5155,9 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
 
 	clear_buddies(cfs_rq, se);
 
+	if (flags & DEQUEUE_SLEEP)
+		update_entity_lag(cfs_rq, se);
+
 	if (se != cfs_rq->curr)
 		__dequeue_entity(cfs_rq, se);
 	se->on_rq = 0;

static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
 	u64 vruntime = avg_vruntime(cfs_rq);
	s64 lag = 0;
 
	/*
	 * Due to how V is constructed as the weighted average of entities,
	 * adding tasks with positive lag, or removing tasks with negative lag
	 * will move 'time' backwards, this can screw around with the lag of
	 * other tasks.
	 *
	 * EEVDF: placement strategy #1 / #2
	 */
	if (sched_feat(PLACE_LAG) && cfs_rq->nr_running > 1) {
		struct sched_entity *curr = cfs_rq->curr;
		unsigned long load;
		lag = se->vlag;

 		/*
		 * If we want to place a task and preserve lag, we have to
		 * consider the effect of the new entity on the weighted
		 * average and compensate for this, otherwise lag can quickly
		 * evaporate.
		 *
		 * Lag is defined as:
		 *
		 *   lag_i = S - s_i = w_i * (V - v_i)
		 *
		 * To avoid the 'w_i' term all over the place, we only track
		 * the virtual lag:
		 *
		 *   vl_i = V - v_i <=> v_i = V - vl_i
		 *
		 * And we take V to be the weighted average of all v:
		 *
		 *   V = (\Sum w_j*v_j) / W
		 *
		 * Where W is: \Sum w_j
		 *
		 * Then, the weighted average after adding an entity with lag
		 * vl_i is given by:
		 *
		 *   V' = (\Sum w_j*v_j + w_i*v_i) / (W + w_i)
		 *      = (W*V + w_i*(V - vl_i)) / (W + w_i)
		 *      = (W*V + w_i*V - w_i*vl_i) / (W + w_i)
		 *      = (V*(W + w_i) - w_i*l) / (W + w_i)
		 *      = V - w_i*vl_i / (W + w_i)
		 *
		 * And the actual lag after adding an entity with vl_i is:
		 *
		 *   vl'_i = V' - v_i
		 *         = V - w_i*vl_i / (W + w_i) - (V - vl_i)
		 *         = vl_i - w_i*vl_i / (W + w_i)
		 *
		 * Which is strictly less than vl_i. So in order to preserve lag
		 * we should inflate the lag before placement such that the
		 * effective lag after placement comes out right.
		 *
		 * As such, invert the above relation for vl'_i to get the vl_i
		 * we need to use such that the lag after placement is the lag
		 * we computed before dequeue.
		 *
		 *   vl'_i = vl_i - w_i*vl_i / (W + w_i)
		 *         = ((W + w_i)*vl_i - w_i*vl_i) / (W + w_i)
		 *
		 *   (W + w_i)*vl'_i = (W + w_i)*vl_i - w_i*vl_i
		 *                   = W*vl_i
		 *
		 *   vl_i = (W + w_i)*vl'_i / W
 		 */
		load = cfs_rq->avg_load;
		if (curr && curr->on_rq)
			load += curr->load.weight;

		lag *= load + se->load.weight;
		if (WARN_ON_ONCE(!load))
			load = 1;
		lag = div_s64(lag, load);

		vruntime -= lag;
 	}

	if (sched_feat(FAIR_SLEEPERS)) {

		/* sleeps up to a single latency don't count. */
		if (!initial) {
			unsigned long thresh;

			if (se_is_idle(se))
				thresh = sysctl_sched_min_granularity;
			else
				thresh = sysctl_sched_latency;

			/*
			 * Halve their sleep time's effect, to allow
			 * for a gentler effect of sleepers:
			 */
			if (sched_feat(GENTLE_FAIR_SLEEPERS))
				thresh >>= 1;

			vruntime -= thresh;
		}

		/*
		 * Pull vruntime of the entity being placed to the base level of
		 * cfs_rq, to prevent boosting it if placed backwards.  If the entity
		 * slept for a long time, don't even try to compare its vruntime with
		 * the base as it may be too far off and the comparison may get
		 * inversed due to s64 overflow.
		 */
		if (!entity_is_long_sleeper(se))
			vruntime = max_vruntime(se->vruntime, vruntime);
	}

	se->vruntime = vruntime;
 }

@@ -1,12 +1,20 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+
 /*
  * Only give sleepers 50% of their service deficit. This allows
  * them to run sooner, but does not allow tons of sleepers to
  * rip the spread apart.
  */
+SCHED_FEAT(FAIR_SLEEPERS, false)
 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
 
 /*
+ * Using the avg_vruntime, do the right thing and preserve lag across
+ * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled.
+ */
+SCHED_FEAT(PLACE_LAG, true)
+
+/*

static __always_inline struct rb_node *
rb_add_augmented_cached(struct rb_node *node, struct rb_root_cached *tree,
			bool (*less)(struct rb_node *, const struct rb_node *),
			const struct rb_augment_callbacks *augment)
{
	struct rb_node **link = &tree->rb_root.rb_node;
	struct rb_node *parent = NULL;
	bool leftmost = true;

	while (*link) {
		parent = *link;
		if (less(node, parent)) {
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = false;
		}
	}

	rb_link_node(node, parent, link);
	augment->propagate(parent, NULL); /* suboptimal */
	rb_insert_augmented_cached(node, tree, leftmost, augment);

	return leftmost ? node : NULL;
}

@@ -550,6 +550,9 @@ struct sched_entity {
 	/* For load-balancing: */
 	struct load_weight		load;
 	struct rb_node			run_node;
+	u64				deadline;
+	u64				min_deadline;
+
 	struct list_head		group_node;
 	unsigned int			on_rq;
 
@@ -558,6 +561,7 @@ struct sched_entity {
 	u64				prev_sum_exec_runtime;
 	u64				vruntime;
 	s64				vlag;
+	u64				slice;
 
 	u64				nr_migrations;

@@ -4464,6 +4464,7 @@ static void __sched_fork(unsigned long c
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
 	p->se.vlag			= 0;
+	p->se.slice			= sysctl_sched_min_granularity;
 	INIT_LIST_HEAD(&p->se.group_node);

@@ -581,9 +581,13 @@ print_task(struct seq_file *m, struct rq
 	else
 		SEQ_printf(m, " %c", task_state_to_char(p));
 
-	SEQ_printf(m, " %15s %5d %9Ld.%06ld %9Ld %5d ",
+	SEQ_printf(m, "%15s %5d %9Ld.%06ld %c %9Ld.%06ld %9Ld.%06ld %9Ld.%06ld %9Ld %5d ",
 		p->comm, task_pid_nr(p),
 		SPLIT_NS(p->se.vruntime),
+		entity_eligible(cfs_rq_of(&p->se), &p->se) ? 'E' : 'N',
+		SPLIT_NS(p->se.deadline),
+		SPLIT_NS(p->se.slice),
+		SPLIT_NS(p->se.sum_exec_runtime),
 		(long long)(p->nvcsw + p->nivcsw),
 		p->prio);
 

 /*
  * lag_i = S - s_i = w_i * (V - v_i)
+ *
+ * However, since V is approximated by the weighted average of all entities it
+ * is possible -- by addition/removal/reweight to the tree -- to move V around
+ * and end up with a larger lag than we started with.
+ *
+ * Limit this to either double the slice length with a minimum of TICK_NSEC
+ * since that is the timing granularity.
+ *
+ * EEVDF gives the following limit for a steady state system:
+ *
+ *   -r_max < lag < max(r_max, q)
+ *
+ * XXX could add max_slice to the augmented data to track this.
  */
 void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
+	s64 lag, limit;
+
 	SCHED_WARN_ON(!se->on_rq);
-	se->vlag = avg_vruntime(cfs_rq) - se->vruntime;
+	lag = avg_vruntime(cfs_rq) - se->vruntime;
+
+	limit = calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se);
+	se->vlag = clamp(lag, -limit, limit);
+}

/*
 * Entity is eligible once it received less service than it ought to have,
 * eg. lag >= 0.
 *
 * lag_i = S - s_i = w_i*(V - v_i)
 *
 * lag_i >= 0 -> V >= v_i
 *
 *     \Sum (v_i - v)*w_i
 * V = ------------------ + v
 *          \Sum w_i
 *
 * lag_i >= 0 -> \Sum (v_i - v)*w_i >= (v_i - v)*(\Sum w_i)
 *
 * Note: using 'avg_vruntime() > se->vruntime' is inacurate due
 *       to the loss in precision caused by the division.
 */
int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct sched_entity *curr = cfs_rq->curr;
	s64 avg = cfs_rq->avg_vruntime;
	long load = cfs_rq->avg_load;

	if (curr && curr->on_rq) {
		unsigned long weight = scale_load_down(curr->load.weight);

		avg += entity_key(cfs_rq, curr) * weight;
		load += weight;
	}

	return avg >= entity_key(cfs_rq, se) * load;
}

@@ -740,8 +802,8 @@ static u64 __update_min_vruntime(struct
 
 static void update_min_vruntime(struct cfs_rq *cfs_rq)
 {
+	struct sched_entity *se = __pick_first_entity(cfs_rq);
 	struct sched_entity *curr = cfs_rq->curr;
-	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
 
 	u64 vruntime = cfs_rq->min_vruntime;
@@ -752,9 +814,7 @@ static void update_min_vruntime(struct c
 			curr = NULL;
 	}
 
-	if (leftmost) { /* non-empty tree */
-		struct sched_entity *se = __node_2_se(leftmost);
-
+	if (se) {
 		if (!curr)
 			vruntime = se->vruntime;

#define deadline_gt(field, lse, rse) ({ (s64)((lse)->field - (rse)->field) > 0; })

static inline void __update_min_deadline(struct sched_entity *se, struct rb_node *node)
{
	if (node) {
		struct sched_entity *rse = __node_2_se(node);
		if (deadline_gt(min_deadline, se, rse))
			se->min_deadline = rse->min_deadline;
	}
}

/*
 * se->min_deadline = min(se->deadline, left->min_deadline, right->min_deadline)
 */
static inline bool min_deadline_update(struct sched_entity *se, bool exit)
{
	u64 old_min_deadline = se->min_deadline;
	struct rb_node *node = &se->run_node;

	se->min_deadline = se->deadline;
	__update_min_deadline(se, node->rb_right);
	__update_min_deadline(se, node->rb_left);

	return se->min_deadline == old_min_deadline;
}

RB_DECLARE_CALLBACKS(static, min_deadline_cb, struct sched_entity,
		     run_node, min_deadline, min_deadline_update);

 /*
  * Enqueue an entity into the rb-tree:
  */
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	avg_vruntime_add(cfs_rq, se);
-	rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
+	se->min_deadline = se->deadline;
+	rb_add_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
+				__entity_less, &min_deadline_cb);
 }

 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
+	rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
+				  &min_deadline_cb);
 	avg_vruntime_sub(cfs_rq, se);
 }

static struct sched_entity *pick_cfs(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
    struct sched_entity *left = __pick_first_entity(cfs_rq);

	/*
	 * If curr is set we have to see if its left of the leftmost entity
	 * still in the tree, provided there was anything in the tree at all.
	 */
	if (!left || (curr && entity_before(curr, left)))
		left = curr;

	return left;
}

/*
 * Earliest Eligible Virtual Deadline First
 *
 * In order to provide latency guarantees for different request sizes
 * EEVDF selects the best runnable task from two criteria:
 *
 *  1) the task must be eligible (must be owed service)
 *
 *  2) from those tasks that meet 1), we select the one
 *     with the earliest virtual deadline.
 *
 * We can do this in O(log n) time due to an augmented RB-tree. The
 * tree keeps the entries sorted on service, but also functions as a
 * heap based on the deadline by keeping:
 *
 *  se->min_deadline = min(se->deadline, se->{left,right}->min_deadline)
 *
 * Which allows an EDF like search on (sub)trees.
 */

static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
{
	struct rb_node *node = cfs_rq->tasks_timeline.rb_root.rb_node;
	struct sched_entity *curr = cfs_rq->curr;
	struct sched_entity *best = NULL;

	if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr)))
		curr = NULL;

	while (node) {
		struct sched_entity *se = __node_2_se(node);

		/*
		 * If this entity is not eligible, try the left subtree.
		 */
		if (!entity_eligible(cfs_rq, se)) {
			node = node->rb_left;
			continue;
		}

		/*
		 * If this entity has an earlier deadline than the previous
		 * best, take this one. If it also has the earliest deadline
		 * of its subtree, we're done.
		 */
		if (!best || deadline_gt(deadline, best, se)) {
			best = se;
			if (best->deadline == best->min_deadline)
				break;
		}

		/*
		 * If the earlest deadline in this subtree is in the fully
		 * eligible left half of our space, go there.
		 */
		if (node->rb_left &&
		    __node_2_se(node->rb_left)->min_deadline == se->min_deadline) {
			node = node->rb_left;
			continue;
		}

		node = node->rb_right;
	}

	if (!best || (curr && deadline_gt(deadline, best, curr)))
		best = curr;

	if (unlikely(!best)) {
		struct sched_entity *left = __pick_first_entity(cfs_rq);
		if (left) {
			pr_err("EEVDF scheduling fail, picking leftmost\n");
			return left;
		}
	}

	return best;
}

static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity se);

/*
 * XXX: strictly: vd_i += N*r_i/w_i such that: vd_i > ve_i
 * this is probably good enough.
 */
static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity se)
{
	if ((s64)(se->vruntime - se->deadline) < 0)
		return;

	if (sched_feat(EEVDF)) {
		/*
		 * For EEVDF the virtual time slope is determined by w_i (iow.
		 * nice) while the request time r_i is determined by
		 * sysctl_sched_min_granularity.
		 */
		se->slice = sysctl_sched_min_granularity;

		/*
		 * The task has consumed its request, reschedule.
		 */
		if (cfs_rq->nr_running > 1) {
			resched_curr(rq_of(cfs_rq));
			clear_buddies(cfs_rq, se);
		}
	} else {
		/*
		 * When many tasks blow up the sched_period; it is possible
		 * that sched_slice() reports unusually large results (when
		 * many tasks are very light for example). Therefore impose a
		 * maximum.
		 */
		se->slice = min_t(u64, sched_slice(cfs_rq, se), sysctl_sched_latency);
	}

	/*
	 * EEVDF: vd_i = ve_i + r_i / w_i
	 */
	se->deadline = se->vruntime + calc_delta_fair(se->slice, se);
}

@@ -1047,6 +1261,7 @@ static void update_curr(struct cfs_rq *c
 	schedstat_add(cfs_rq->exec_clock, delta_exec);
 
 	curr->vruntime += calc_delta_fair(delta_exec, curr);
+	update_deadline(cfs_rq, curr);
 	update_min_vruntime(cfs_rq);

@@ -3521,6 +3736,14 @@ static void reweight_entity(struct cfs_r
 		 * we need to scale se->vlag when w_i changes.
 		 */
 		se->vlag = div_s64(se->vlag * old_weight, weight);
+	} else {
+		s64 deadline = se->deadline - se->vruntime;
+		/*
+		 * When the weight changes, the virtual time slope changes and
+		 * we should adjust the relative virtual deadline accordingly.
+		 */
+		deadline = div_s64(deadline * old_weight, weight);
+		se->deadline = se->vruntime + deadline;
 	}

@@ -4871,6 +5094,7 @@ static inline bool entity_is_long_sleepe
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
+	u64 vslice = calc_delta_fair(se->slice, se);
 	u64 vruntime = avg_vruntime(cfs_rq);
 	s64 lag = 0;
 
@@ -4942,9 +5166,9 @@ place_entity(struct cfs_rq *cfs_rq, stru
 		 */
 		load = cfs_rq->avg_load;
 		if (curr && curr->on_rq)
-			load += curr->load.weight;
+			load += scale_load_down(curr->load.weight);
 
-		lag *= load + se->load.weight;
+		lag *= load + scale_load_down(se->load.weight);
 		if (WARN_ON_ONCE(!load))
 			load = 1;
 		lag = div_s64(lag, load);

@@ -4985,6 +5209,19 @@ place_entity(struct cfs_rq *cfs_rq, stru
 	}
 
 	se->vruntime = vruntime;
+
+	/*
+	 * When joining the competition; the exisiting tasks will be,
+	 * on average, halfway through their slice, as such start tasks
+	 * off with half a slice to ease into the competition.
+	 */
+	if (sched_feat(PLACE_DEADLINE_INITIAL) && initial)
+		vslice /= 2;
+
+	/*
+	 * EEVDF: vd_i = ve_i + r_i/w_i
+	 */
+	se->deadline = se->vruntime + vslice;
 }

@@ -5196,19 +5433,12 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
 static void
 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
-	unsigned long ideal_runtime, delta_exec;
+	unsigned long delta_exec;
 	struct sched_entity *se;
 	s64 delta;
 
-	/*
-	 * When many tasks blow up the sched_period; it is possible that
-	 * sched_slice() reports unusually large results (when many tasks are
-	 * very light for example). Therefore impose a maximum.
-	 */
-	ideal_runtime = min_t(u64, sched_slice(cfs_rq, curr), sysctl_sched_latency);
-
 	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
-	if (delta_exec > ideal_runtime) {
+	if (delta_exec > curr->slice) {

@@ -5287,17 +5517,20 @@ wakeup_preempt_entity(struct sched_entit
 static struct sched_entity *
 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
-	struct sched_entity *left = __pick_first_entity(cfs_rq);
-	struct sched_entity *se;
+	struct sched_entity *left, *se;
 
-	/*
-	 * If curr is set we have to see if its left of the leftmost entity
-	 * still in the tree, provided there was anything in the tree at all.
-	 */
-	if (!left || (curr && entity_before(curr, left)))
-		left = curr;
+	if (sched_feat(EEVDF)) {
+		/*
+		 * Enabling NEXT_BUDDY will affect latency but not fairness.
+		 */
+		if (sched_feat(NEXT_BUDDY) &&
+		    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
+			return cfs_rq->next;
+
+		return pick_eevdf(cfs_rq);
+	}
 
-	se = left; /* ideally we run the leftmost entity */
+	se = left = pick_cfs(cfs_rq, curr);

@@ -5390,7 +5623,7 @@ entity_tick(struct cfs_rq *cfs_rq, struc
 		return;
 #endif
 
-	if (cfs_rq->nr_running > 1)
+	if (!sched_feat(EEVDF) && cfs_rq->nr_running > 1)
 		check_preempt_tick(cfs_rq, curr);
 }

@@ -6396,13 +6629,12 @@ static inline void unthrottle_offline_cf
 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
 {
 	struct sched_entity *se = &p->se;
-	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
 	SCHED_WARN_ON(task_rq(p) != rq);
 
 	if (rq->cfs.h_nr_running > 1) {
-		u64 slice = sched_slice(cfs_rq, se);
 		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
+		u64 slice = se->slice;
 		s64 delta = slice - ran;
 
 		if (delta < 0) {

@@ -8122,7 +8354,19 @@ static void check_preempt_wakeup(struct
 	if (cse_is_idle != pse_is_idle)
 		return;
 
-	update_curr(cfs_rq_of(se));
+	cfs_rq = cfs_rq_of(se);
+	update_curr(cfs_rq);
+
+	if (sched_feat(EEVDF)) {
+		/*
+		 * XXX pick_eevdf(cfs_rq) != se ?
+		 */
+		if (pick_eevdf(cfs_rq) == pse)
+			goto preempt;
+
+		return;
+	}
+
 	if (wakeup_preempt_entity(se, pse) == 1) {
 		/*
 		 * Bias pick_next to pick the sched entity that is

@@ -8368,7 +8612,7 @@ static void yield_task_fair(struct rq *r
 
 	clear_buddies(cfs_rq, se);
 
-	if (curr->policy != SCHED_BATCH) {
+	if (sched_feat(EEVDF) || curr->policy != SCHED_BATCH) {
 		update_rq_clock(rq);
 		/*
 		 * Update run-time statistics of the 'current'.
@@ -8381,6 +8625,8 @@ static void yield_task_fair(struct rq *r
 		 */
 		rq_clock_skip_update(rq);
 	}
+	if (sched_feat(EEVDF))
+		se->deadline += calc_delta_fair(se->slice, se);
 
 	set_skip_buddy(se);
 }

@@ -12136,8 +12382,8 @@ static void rq_offline_fair(struct rq *r
 static inline bool
 __entity_slice_used(struct sched_entity *se, int min_nr_tasks)
 {
-	u64 slice = sched_slice(cfs_rq_of(se), se);
 	u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime;
+	u64 slice = se->slice;
 
 	return (rtime * min_nr_tasks > slice);
 }
@@ -12832,7 +13078,7 @@ static unsigned int get_rr_interval_fair
 	 * idle runqueue:
 	 */
 	if (rq->cfs.load.weight)
-		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
+		rr_interval = NS_TO_JIFFIES(se->slice);
 
 	return rr_interval;
 }

--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -13,6 +13,7 @@ SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
  * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled.
  */
 SCHED_FEAT(PLACE_LAG, true)
+SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 
 /*
  * Prefer to schedule the task we woke last (assuming it failed
@@ -103,3 +104,5 @@ SCHED_FEAT(LATENCY_WARN, false)
 
 SCHED_FEAT(ALT_PERIOD, true)
 SCHED_FEAT(BASE_SLICE, true)
+
+SCHED_FEAT(EEVDF, true)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2481,9 +2481,10 @@ extern void check_preempt_curr(struct rq
 extern const_debug unsigned int sysctl_sched_nr_migrate;
 extern const_debug unsigned int sysctl_sched_migration_cost;
 
+extern unsigned int sysctl_sched_min_granularity;
+
 #ifdef CONFIG_SCHED_DEBUG
 extern unsigned int sysctl_sched_latency;
-extern unsigned int sysctl_sched_min_granularity;
 extern unsigned int sysctl_sched_idle_min_granularity;
 extern unsigned int sysctl_sched_wakeup_granularity;
 extern int sysctl_resched_latency_warn_ms;
@@ -3507,5 +3508,6 @@ static inline void init_sched_mm_cid(str
 #endif
 
 extern u64 avg_vruntime(struct cfs_rq *cfs_rq);
+extern int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se);
 
 #endif /* _KERNEL_SCHED_SCHED_H */

-/*
- * MIGRATION
- *
- *	dequeue
- *	  update_curr()
- *	    update_min_vruntime()
- *	  vruntime -= min_vruntime
- *
- *	enqueue
- *	  update_curr()
- *	    update_min_vruntime()
- *	  vruntime += min_vruntime
- *
- * this way the vruntime transition between RQs is done when both
- * min_vruntime are up-to-date.
- *
- * WAKEUP (remote)
- *
- *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
- *	  vruntime -= min_vruntime
- *
- *	enqueue
- *	  update_curr()
- *	    update_min_vruntime()
- *	  vruntime += min_vruntime
- *
- * this way we don't have the most up-to-date min_vruntime on the originating
- * CPU and an up-to-date min_vruntime on the destination CPU.
- */
-

 static void
 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
-	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
 	bool curr = cfs_rq->curr == se;
 
 	/*
 	 * If we're the current task, we must renormalise before calling
 	 * update_curr().
 	 */
-	if (renorm && curr)
-		se->vruntime += cfs_rq->min_vruntime;
+	if (curr)
+		place_entity(cfs_rq, se, 0);
 
 	update_curr(cfs_rq);
 
 	/*
-	 * Otherwise, renormalise after, such that we're placed at the current
-	 * moment in time, instead of some random moment in the past. Being
-	 * placed in the past could significantly boost this task to the
-	 * fairness detriment of existing tasks.
-	 */
-	if (renorm && !curr)
-		se->vruntime += cfs_rq->min_vruntime;
-
-	/*
 	 * When enqueuing a sched_entity, we must:
 	 *   - Update loads to have both entity and cfs_rq synced with now.
 	 *   - For group_entity, update its runnable_weight to reflect the new
@@ -5236,11 +5196,22 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
 	 */
 	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
 	se_update_runnable(se);
+	/*
+	 * XXX update_load_avg() above will have attached us to the pelt sum;
+	 * but update_cfs_group() here will re-adjust the weight and have to
+	 * undo/redo all that. Seems wasteful.
+	 */
 	update_cfs_group(se);
-	account_entity_enqueue(cfs_rq, se);
 
-	if (flags & ENQUEUE_WAKEUP)
+	/*
+	 * XXX now that the entity has been re-weighted, and it's lag adjusted,
+	 * we can place the entity.
+	 */
+	if (!curr)
 		place_entity(cfs_rq, se, 0);
+
+	account_entity_enqueue(cfs_rq, se);
+
 	/* Entity has migrated, no longer consider this task hot */
 	if (flags & ENQUEUE_MIGRATED)
 		se->exec_start = 0;

@@ -5335,23 +5306,12 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
 
 	clear_buddies(cfs_rq, se);
 
-	if (flags & DEQUEUE_SLEEP)
-		update_entity_lag(cfs_rq, se);
-
+	update_entity_lag(cfs_rq, se);
 	if (se != cfs_rq->curr)
 		__dequeue_entity(cfs_rq, se);
 	se->on_rq = 0;
 	account_entity_dequeue(cfs_rq, se);
 
-	/*
-	 * Normalize after update_curr(); which will also have moved
-	 * min_vruntime if @se is the one holding it back. But before doing
-	 * update_min_vruntime() again, which will discount @se's position and
-	 * can move min_vruntime forward still more.
-	 */
-	if (!(flags & DEQUEUE_SLEEP))
-		se->vruntime -= cfs_rq->min_vruntime;
-
 	/* return excess runtime on last dequeue */
 	return_cfs_rq_runtime(cfs_rq);
 

@@ -8102,18 +8062,6 @@ static void migrate_task_rq_fair(struct
 {
 	struct sched_entity *se = &p->se;
 
-	/*
-	 * As blocked tasks retain absolute vruntime the migration needs to
-	 * deal with this by subtracting the old and adding the new
-	 * min_vruntime -- the latter is done by enqueue_entity() when placing
-	 * the task on the new runqueue.
-	 */
-	if (READ_ONCE(p->__state) == TASK_WAKING) {
-		struct cfs_rq *cfs_rq = cfs_rq_of(se);
-
-		se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
-	}
-
 	if (!task_on_rq_migrating(p)) {
 		remove_entity_load_avg(se);

@@ -12492,22 +12440,9 @@ static void task_fork_fair(struct task_s
 
 	cfs_rq = task_cfs_rq(current);
 	curr = cfs_rq->curr;
-	if (curr) {
+	if (curr)
 		update_curr(cfs_rq);
-		se->vruntime = curr->vruntime;
-	}
 	place_entity(cfs_rq, se, 1);
-
-	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
-		/*
-		 * Upon rescheduling, sched_class::put_prev_task() will place
-		 * 'current' within the tree based on its new key value.
-		 */
-		swap(curr->vruntime, se->vruntime);
-		resched_curr(rq);
-	}
-
-	se->vruntime -= cfs_rq->min_vruntime;
 	rq_unlock(rq, &rf);
 }

@@ -12536,34 +12471,6 @@ prio_changed_fair(struct rq *rq, struct
 		check_preempt_curr(rq, p, 0);
 }
 
-static inline bool vruntime_normalized(struct task_struct *p)
-{
-	struct sched_entity *se = &p->se;
-
-	/*
-	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
-	 * the dequeue_entity(.flags=0) will already have normalized the
-	 * vruntime.
-	 */
-	if (p->on_rq)
-		return true;
-
-	/*
-	 * When !on_rq, vruntime of the task has usually NOT been normalized.
-	 * But there are some cases where it has already been normalized:
-	 *
-	 * - A forked child which is waiting for being woken up by
-	 *   wake_up_new_task().
-	 * - A task which has been woken up by try_to_wake_up() and
-	 *   waiting for actually being woken up by sched_ttwu_pending().
-	 */
-	if (!se->sum_exec_runtime ||
-	    (READ_ONCE(p->__state) == TASK_WAKING && p->sched_remote_wakeup))
-		return true;
-
-	return false;
-}
-

@@ -12634,16 +12541,6 @@ static void attach_entity_cfs_rq(struct
 static void detach_task_cfs_rq(struct task_struct *p)
 {
 	struct sched_entity *se = &p->se;
-	struct cfs_rq *cfs_rq = cfs_rq_of(se);
-
-	if (!vruntime_normalized(p)) {
-		/*
-		 * Fix up our vruntime so that the current sleep doesn't
-		 * cause 'unlimited' sleep bonus.
-		 */
-		place_entity(cfs_rq, se, 0);
-		se->vruntime -= cfs_rq->min_vruntime;
-	}
 
 	detach_entity_cfs_rq(se);
 }
@@ -12651,12 +12548,8 @@ static void detach_task_cfs_rq(struct ta
 static void attach_task_cfs_rq(struct task_struct *p)
 {
 	struct sched_entity *se = &p->se;
-	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
 	attach_entity_cfs_rq(se);
-
-	if (!vruntime_normalized(p))
-		se->vruntime += cfs_rq->min_vruntime;
 }
 

--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -347,10 +347,7 @@ static __init int sched_init_debug(void)
 	debugfs_create_file("preempt", 0644, debugfs_sched, NULL, &sched_dynamic_fops);
 #endif
 
-	debugfs_create_u32("latency_ns", 0644, debugfs_sched, &sysctl_sched_latency);
 	debugfs_create_u32("min_granularity_ns", 0644, debugfs_sched, &sysctl_sched_min_granularity);
-	debugfs_create_u32("idle_min_granularity_ns", 0644, debugfs_sched, &sysctl_sched_idle_min_granularity);
-	debugfs_create_u32("wakeup_granularity_ns", 0644, debugfs_sched, &sysctl_sched_wakeup_granularity);
 
 	debugfs_create_u32("latency_warn_ms", 0644, debugfs_sched, &sysctl_resched_latency_warn_ms);
 	debugfs_create_u32("latency_warn_once", 0644, debugfs_sched, &sysctl_resched_latency_warn_once);
@@ -865,10 +862,7 @@ static void sched_debug_header(struct se
 	SEQ_printf(m, "  .%-40s: %Ld\n", #x, (long long)(x))
 #define PN(x) \
 	SEQ_printf(m, "  .%-40s: %Ld.%06ld\n", #x, SPLIT_NS(x))
-	PN(sysctl_sched_latency);
 	PN(sysctl_sched_min_granularity);
-	PN(sysctl_sched_idle_min_granularity);
-	PN(sysctl_sched_wakeup_granularity);
 	P(sysctl_sched_child_runs_first);
 	P(sysctl_sched_features);
 #undef PN

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -58,22 +58,6 @@
 #include "autogroup.h"
 
 /*
- * Targeted preemption latency for CPU-bound tasks:
- *
- * NOTE: this latency value is not the same as the concept of
- * 'timeslice length' - timeslices in CFS are of variable length
- * and have no persistent notion like in traditional, time-slice
- * based scheduling concepts.
- *
- * (to see the precise effective timeslice length of your workload,
- *  run vmstat and monitor the context-switches (cs) field)
- *
- * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
- */
-unsigned int sysctl_sched_latency			= 6000000ULL;
-static unsigned int normalized_sysctl_sched_latency	= 6000000ULL;
-
-/*
  * The initial- and re-scaling of tunables is configurable
  *
  * Options are:
@@ -95,36 +79,11 @@ unsigned int sysctl_sched_min_granularit
 static unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
 
 /*
- * Minimal preemption granularity for CPU-bound SCHED_IDLE tasks.
- * Applies only when SCHED_IDLE tasks compete with normal tasks.
- *
- * (default: 0.75 msec)
- */
-unsigned int sysctl_sched_idle_min_granularity			= 750000ULL;
-
-/*
- * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
- */
-static unsigned int sched_nr_latency = 8;
-
-/*
  * After fork, child runs first. If set to 0 (default) then
  * parent will (try to) run first.
  */
 unsigned int sysctl_sched_child_runs_first __read_mostly;
 
-/*
- * SCHED_OTHER wake-up granularity.
- *
- * This option delays the preemption effects of decoupled workloads
- * and reduces their over-scheduling. Synchronous workloads will still
- * have immediate wakeup/sleep latencies.
- *
- * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
- */
-unsigned int sysctl_sched_wakeup_granularity			= 1000000UL;
-static unsigned int normalized_sysctl_sched_wakeup_granularity	= 1000000UL;
-
 const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
 
 int sched_thermal_decay_shift;
@@ -279,8 +238,6 @@ static void update_sysctl(void)
 #define SET_SYSCTL(name) \
 	(sysctl_##name = (factor) * normalized_sysctl_##name)
 	SET_SYSCTL(sched_min_granularity);
-	SET_SYSCTL(sched_latency);
-	SET_SYSCTL(sched_wakeup_granularity);
 #undef SET_SYSCTL
 }

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -576,8 +576,6 @@ struct cfs_rq {
 	 */
 	struct sched_entity	*curr;
 	struct sched_entity	*next;
-	struct sched_entity	*last;
-	struct sched_entity	*skip;
 

-static struct sched_entity *__pick_next_entity(struct sched_entity *se)
-{
-	struct rb_node *next = rb_next(&se->run_node);
-
-	if (!next)
-		return NULL;
-
-	return __node_2_se(next);
-}

-static struct sched_entity *pick_cfs(struct cfs_rq *cfs_rq, struct sched_entity *curr)
-{
-	struct sched_entity *left = __pick_first_entity(cfs_rq);
-
-	/*
-	 * If curr is set we have to see if its left of the leftmost entity
-	 * still in the tree, provided there was anything in the tree at all.
-	 */
-	if (!left || (curr && entity_before(curr, left)))
-		left = curr;
-
-	return left;
-}

 /*
  * Earliest Eligible Virtual Deadline First
  *
@@ -1008,85 +941,15 @@ int sched_update_scaling(void)
 {
 	unsigned int factor = get_update_sysctl_factor();
 
-	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
-					sysctl_sched_min_granularity);
-
 #define WRT_SYSCTL(name) \
 	(normalized_sysctl_##name = sysctl_##name / (factor))
 	WRT_SYSCTL(sched_min_granularity);
-	WRT_SYSCTL(sched_latency);
-	WRT_SYSCTL(sched_wakeup_granularity);
 #undef WRT_SYSCTL
 
 	return 0;
 }
 #endif

-/*
- * The idea is to set a period in which each task runs once.
- *
- * When there are too many tasks (sched_nr_latency) we have to stretch
- * this period because otherwise the slices get too small.
- *
- * p = (nr <= nl) ? l : l*nr/nl
- */
-static u64 __sched_period(unsigned long nr_running)
-{
-	if (unlikely(nr_running > sched_nr_latency))
-		return nr_running * sysctl_sched_min_granularity;
-	else
-		return sysctl_sched_latency;
-}
-
-
-static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq);
-
-/*
- * We calculate the wall-time slice from the period by taking a part
- * proportional to the weight.
- *
- * s = p*P[w/rw]
- */
-static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-	unsigned int nr_running = cfs_rq->nr_running;
-	struct sched_entity *init_se = se;
-	unsigned int min_gran;
-	u64 slice;
-
-	if (sched_feat(ALT_PERIOD))
-		nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
-
-	slice = __sched_period(nr_running + !se->on_rq);
-
-	for_each_sched_entity(se) {
-		struct load_weight *load;
-		struct load_weight lw;
-		struct cfs_rq *qcfs_rq;
-
-		qcfs_rq = cfs_rq_of(se);
-		load = &qcfs_rq->load;
-
-		if (unlikely(!se->on_rq)) {
-			lw = qcfs_rq->load;
-
-			update_load_add(&lw, se->load.weight);
-			load = &lw;
-		}
-		slice = __calc_delta(slice, se->load.weight, load);
-	}
-
-	if (sched_feat(BASE_SLICE)) {
-		if (se_is_idle(init_se) && !sched_idle_cfs_rq(cfs_rq))
-			min_gran = sysctl_sched_idle_min_granularity;
-		else
-			min_gran = sysctl_sched_min_granularity;
-
-		slice = max_t(u64, slice, min_gran);
-	}
-
-	return slice;
-}
-

@@ -1098,35 +961,25 @@ static void update_deadline(struct cfs_r
 	if ((s64)(se->vruntime - se->deadline) < 0)
 		return;
 
-	if (sched_feat(EEVDF)) {
-		/*
-		 * For EEVDF the virtual time slope is determined by w_i (iow.
-		 * nice) while the request time r_i is determined by
-		 * sysctl_sched_min_granularity.
-		 */
-		se->slice = sysctl_sched_min_granularity;
-
-		/*
-		 * The task has consumed its request, reschedule.
-		 */
-		if (cfs_rq->nr_running > 1) {
-			resched_curr(rq_of(cfs_rq));
-			clear_buddies(cfs_rq, se);
-		}
-	} else {
-		/*
-		 * When many tasks blow up the sched_period; it is possible
-		 * that sched_slice() reports unusually large results (when
-		 * many tasks are very light for example). Therefore impose a
-		 * maximum.
-		 */
-		se->slice = min_t(u64, sched_slice(cfs_rq, se), sysctl_sched_latency);
-	}
+	/*
+	 * For EEVDF the virtual time slope is determined by w_i (iow.
+	 * nice) while the request time r_i is determined by
+	 * sysctl_sched_min_granularity.
+	 */
+	se->slice = sysctl_sched_min_granularity;
 
 	/*
 	 * EEVDF: vd_i = ve_i + r_i / w_i
 	 */
 	se->deadline = se->vruntime + calc_delta_fair(se->slice, se);
+
+	/*
+	 * The task has consumed its request, reschedule.
+	 */
+	if (cfs_rq->nr_running > 1) {
+		resched_curr(rq_of(cfs_rq));
+		clear_buddies(cfs_rq, se);
+	}
 }

-static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-#ifdef CONFIG_SCHED_DEBUG
-	s64 d = se->vruntime - cfs_rq->min_vruntime;
-
-	if (d < 0)
-		d = -d;
-
-	if (d > 3*sysctl_sched_latency)
-		schedstat_inc(cfs_rq->nr_spread_over);
-#endif
-}
-
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
@@ -5218,7 +5058,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
 
 	check_schedstat_required();
 	update_stats_enqueue_fair(cfs_rq, se, flags);
-	check_spread(cfs_rq, se);
 	if (!curr)
 		__enqueue_entity(cfs_rq, se);
 	se->on_rq = 1;
@@ -5230,17 +5069,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
 	}
 }

-static void __clear_buddies_last(struct sched_entity *se)
-{
-	for_each_sched_entity(se) {
-		struct cfs_rq *cfs_rq = cfs_rq_of(se);
-		if (cfs_rq->last != se)
-			break;
-
-		cfs_rq->last = NULL;
-	}
-}
-
 static void __clear_buddies_next(struct sched_entity *se)
 {
 	for_each_sched_entity(se) {
@@ -5252,27 +5080,10 @@ static void __clear_buddies_next(struct
 	}
 }
 
-static void __clear_buddies_skip(struct sched_entity *se)
-{
-	for_each_sched_entity(se) {
-		struct cfs_rq *cfs_rq = cfs_rq_of(se);
-		if (cfs_rq->skip != se)
-			break;
-
-		cfs_rq->skip = NULL;
-	}
-}
-
 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	if (cfs_rq->last == se)
-		__clear_buddies_last(se);
-
 	if (cfs_rq->next == se)
 		__clear_buddies_next(se);
-
-	if (cfs_rq->skip == se)
-		__clear_buddies_skip(se);
 }

-/*
- * Preempt the current task with a newly woken task if needed:
- */
-static void
-check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
-{
-	unsigned long delta_exec;
-	struct sched_entity *se;
-	s64 delta;
-
-	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
-	if (delta_exec > curr->slice) {
-		resched_curr(rq_of(cfs_rq));
-		/*
-		 * The current task ran long enough, ensure it doesn't get
-		 * re-elected due to buddy favours.
-		 */
-		clear_buddies(cfs_rq, curr);
-		return;
-	}
-
-	/*
-	 * Ensure that a task that missed wakeup preemption by a
-	 * narrow margin doesn't have to wait for a full slice.
-	 * This also mitigates buddy induced latencies under load.
-	 */
-	if (delta_exec < sysctl_sched_min_granularity)
-		return;
-
-	se = __pick_first_entity(cfs_rq);
-	delta = curr->vruntime - se->vruntime;
-
-	if (delta < 0)
-		return;
-
-	if (delta > curr->slice)
-		resched_curr(rq_of(cfs_rq));
-}
-

 /*
  * Pick the next process, keeping these things in mind, in this order:
  * 1) keep things fair between processes/task groups
@@ -5420,53 +5189,14 @@ wakeup_preempt_entity(struct sched_entit
 static struct sched_entity *
 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
-	struct sched_entity *left, *se;
-
-	if (sched_feat(EEVDF)) {
-		/*
-		 * Enabling NEXT_BUDDY will affect latency but not fairness.
-		 */
-		if (sched_feat(NEXT_BUDDY) &&
-		    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
-			return cfs_rq->next;
-
-		return pick_eevdf(cfs_rq);
-	}
-
-	se = left = pick_cfs(cfs_rq, curr);
-
 	/*
-	 * Avoid running the skip buddy, if running something else can
-	 * be done without getting too unfair.
+	 * Enabling NEXT_BUDDY will affect latency but not fairness.
 	 */
-	if (cfs_rq->skip && cfs_rq->skip == se) {
-		struct sched_entity *second;
+	if (sched_feat(NEXT_BUDDY) &&
+	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
+		return cfs_rq->next;
 
-		if (se == curr) {
-			second = __pick_first_entity(cfs_rq);
-		} else {
-			second = __pick_next_entity(se);
-			if (!second || (curr && entity_before(curr, second)))
-				second = curr;
-		}
-
-		if (second && wakeup_preempt_entity(second, left) < 1)
-			se = second;
-	}
-
-	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
-		/*
-		 * Someone really wants this to run. If it's not unfair, run it.
-		 */
-		se = cfs_rq->next;
-	} else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
-		/*
-		 * Prefer last buddy, try to return the CPU to a preempted task.
-		 */
-		se = cfs_rq->last;
-	}
-
-	return se;
+	return pick_eevdf(cfs_rq);
 }

 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
@@ -5483,8 +5213,6 @@ static void put_prev_entity(struct cfs_r
 	/* throttle cfs_rqs exceeding runtime */
 	check_cfs_rq_runtime(cfs_rq);
 
-	check_spread(cfs_rq, prev);
-

@@ -5525,9 +5253,6 @@ entity_tick(struct cfs_rq *cfs_rq, struc
 			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
 		return;
 #endif
-
-	if (!sched_feat(EEVDF) && cfs_rq->nr_running > 1)
-		check_preempt_tick(cfs_rq, curr);
 }
 

@@ -6561,8 +6286,7 @@ static void hrtick_update(struct rq *rq)
 	if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
 		return;
 
-	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
-		hrtick_start_fair(rq, curr);
+	hrtick_start_fair(rq, curr);
 }

-/*
- * Returns true if cfs_rq only has SCHED_IDLE entities enqueued. Note the use
- * of idle_nr_running, which does not consider idle descendants of normal
- * entities.
- */
-static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq)
-{
-	return cfs_rq->nr_running &&
-		cfs_rq->nr_running == cfs_rq->idle_nr_running;
-}
-

@@ -8099,66 +7812,6 @@ balance_fair(struct rq *rq, struct task_
 }
 #endif /* CONFIG_SMP */
 
-static unsigned long wakeup_gran(struct sched_entity *se)
-{
-	unsigned long gran = sysctl_sched_wakeup_granularity;
-
-	/*
-	 * Since its curr running now, convert the gran from real-time
-	 * to virtual-time in his units.
-	 *
-	 * By using 'se' instead of 'curr' we penalize light tasks, so
-	 * they get preempted easier. That is, if 'se' < 'curr' then
-	 * the resulting gran will be larger, therefore penalizing the
-	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
-	 * be smaller, again penalizing the lighter task.
-	 *
-	 * This is especially important for buddies when the leftmost
-	 * task is higher priority than the buddy.
-	 */
-	return calc_delta_fair(gran, se);
-}
-
-/*
- * Should 'se' preempt 'curr'.
- *
- *             |s1
- *        |s2
- *   |s3
- *         g
- *      |<--->|c
- *
- *  w(c, s1) = -1
- *  w(c, s2) =  0
- *  w(c, s3) =  1
- *
- */
-static int
-wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
-{
-	s64 gran, vdiff = curr->vruntime - se->vruntime;
-
-	if (vdiff <= 0)
-		return -1;
-
-	gran = wakeup_gran(se);
-	if (vdiff > gran)
-		return 1;
-
-	return 0;
-}
-
-static void set_last_buddy(struct sched_entity *se)
-{
-	for_each_sched_entity(se) {
-		if (SCHED_WARN_ON(!se->on_rq))
-			return;
-		if (se_is_idle(se))
-			return;
-		cfs_rq_of(se)->last = se;
-	}
-}
-
 static void set_next_buddy(struct sched_entity *se)
 {
 	for_each_sched_entity(se) {
@@ -8170,12 +7823,6 @@ static void set_next_buddy(struct sched_
 	}
 }
 
-static void set_skip_buddy(struct sched_entity *se)
-{
-	for_each_sched_entity(se)
-		cfs_rq_of(se)->skip = se;
-}
-

@@ -8184,7 +7831,6 @@ static void check_preempt_wakeup(struct
 	struct task_struct *curr = rq->curr;
 	struct sched_entity *se = &curr->se, *pse = &p->se;
 	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
-	int scale = cfs_rq->nr_running >= sched_nr_latency;
 	int next_buddy_marked = 0;
 	int cse_is_idle, pse_is_idle;
 
@@ -8200,7 +7846,7 @@ static void check_preempt_wakeup(struct
 	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
 		return;
 
-	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
+	if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) {
 		set_next_buddy(pse);
 		next_buddy_marked = 1;
 	}

@@ -8248,44 +7894,16 @@ static void check_preempt_wakeup(struct
 	cfs_rq = cfs_rq_of(se);
 	update_curr(cfs_rq);
 
-	if (sched_feat(EEVDF)) {
-		/*
-		 * XXX pick_eevdf(cfs_rq) != se ?
-		 */
-		if (pick_eevdf(cfs_rq) == pse)
-			goto preempt;
-
-		return;
-	}
-
-	if (wakeup_preempt_entity(se, pse) == 1) {
-		/*
-		 * Bias pick_next to pick the sched entity that is
-		 * triggering this preemption.
-		 */
-		if (!next_buddy_marked)
-			set_next_buddy(pse);
+	/*
+	 * XXX pick_eevdf(cfs_rq) != se ?
+	 */
+	if (pick_eevdf(cfs_rq) == pse)
 		goto preempt;
-	}
 
 	return;
 
 preempt:
 	resched_curr(rq);
-	/*
-	 * Only set the backward buddy when the current task is still
-	 * on the rq. This can happen when a wakeup gets interleaved
-	 * with schedule on the ->pre_schedule() or idle_balance()
-	 * point, either of which can * drop the rq lock.
-	 *
-	 * Also, during early boot the idle thread is in the fair class,
-	 * for obvious reasons its a bad idea to schedule back to it.
-	 */
-	if (unlikely(!se->on_rq || curr == rq->idle))
-		return;
-
-	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
-		set_last_buddy(se);
 }
 
 #ifdef CONFIG_SMP
@@ -8486,8 +8104,6 @@ static void put_prev_task_fair(struct rq
 
 /*
  * sched_yield() is very simple
- *
- * The magic of dealing with the ->skip buddy is in pick_next_entity.
  */
 static void yield_task_fair(struct rq *rq)
 {
@@ -8503,23 +8119,19 @@ static void yield_task_fair(struct rq *r
 
 	clear_buddies(cfs_rq, se);
 
-	if (sched_feat(EEVDF) || curr->policy != SCHED_BATCH) {
-		update_rq_clock(rq);
-		/*
-		 * Update run-time statistics of the 'current'.
-		 */
-		update_curr(cfs_rq);
-		/*
-		 * Tell update_rq_clock() that we've just updated,
-		 * so we don't do microscopic update in schedule()
-		 * and double the fastpath cost.
-		 */
-		rq_clock_skip_update(rq);
-	}
-	if (sched_feat(EEVDF))
-		se->deadline += calc_delta_fair(se->slice, se);
+	update_rq_clock(rq);
+	/*
+	 * Update run-time statistics of the 'current'.
+	 */
+	update_curr(cfs_rq);
+	/*
+	 * Tell update_rq_clock() that we've just updated,
+	 * so we don't do microscopic update in schedule()
+	 * and double the fastpath cost.
+	 */
+	rq_clock_skip_update(rq);
 
-	set_skip_buddy(se);
+	se->deadline += calc_delta_fair(se->slice, se);
 }
 
 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
@@ -8762,8 +8374,7 @@ static int task_hot(struct task_struct *
 	 * Buddy candidates are cache hot:
 	 */
 	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
-			(&p->se == cfs_rq_of(&p->se)->next ||
-			 &p->se == cfs_rq_of(&p->se)->last))
+	    (&p->se == cfs_rq_of(&p->se)->next))
 		return 1;

--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -15,13 +15,6 @@ SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 SCHED_FEAT(NEXT_BUDDY, false)
 
 /*
- * Prefer to schedule the task that ran last (when we did
- * wake-preempt) as that likely will touch the same data, increases
- * cache locality.
- */
-SCHED_FEAT(LAST_BUDDY, true)
-
-/*
  * Consider buddies to be cache hot, decreases the likeliness of a
  * cache buddy being migrated away, increases cache locality.
  */
@@ -93,8 +86,3 @@ SCHED_FEAT(UTIL_EST, true)
 SCHED_FEAT(UTIL_EST_FASTUP, true)
 
 SCHED_FEAT(LATENCY_WARN, false)
-
-SCHED_FEAT(ALT_PERIOD, true)
-SCHED_FEAT(BASE_SLICE, true)
-
-SCHED_FEAT(EEVDF, true)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -576,8 +576,6 @@ struct cfs_rq {
 	 */
 	struct sched_entity	*curr;
 	struct sched_entity	*next;
-	struct sched_entity	*last;
-	struct sched_entity	*skip;
 
 #ifdef	CONFIG_SCHED_DEBUG
 	unsigned int		nr_spread_over;
@@ -2484,9 +2482,6 @@ extern const_debug unsigned int sysctl_s
 extern unsigned int sysctl_sched_min_granularity;
 
 #ifdef CONFIG_SCHED_DEBUG
-extern unsigned int sysctl_sched_latency;
-extern unsigned int sysctl_sched_idle_min_granularity;
-extern unsigned int sysctl_sched_wakeup_granularity;
 extern int sysctl_resched_latency_warn_ms;
 extern int sysctl_resched_latency_warn_once;

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4909,7 +4909,7 @@ static inline void update_misfit_status(
 #endif /* CONFIG_SMP */
 
 static void
-place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
+place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
 	u64 vslice = calc_delta_fair(se->slice, se);
 	u64 vruntime = avg_vruntime(cfs_rq);
@@ -4998,7 +4998,7 @@ place_entity(struct cfs_rq *cfs_rq, stru
 	 * on average, halfway through their slice, as such start tasks
 	 * off with half a slice to ease into the competition.
 	 */
-	if (sched_feat(PLACE_DEADLINE_INITIAL) && initial)
+	if (sched_feat(PLACE_DEADLINE_INITIAL) && (flags & ENQUEUE_INITIAL))
 		vslice /= 2;
 
 	/*
@@ -5021,7 +5021,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
 	 * update_curr().
 	 */
 	if (curr)
-		place_entity(cfs_rq, se, 0);
+		place_entity(cfs_rq, se, flags);
 
 	update_curr(cfs_rq);
 
@@ -5048,7 +5048,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, st
 	 * we can place the entity.
 	 */
 	if (!curr)
-		place_entity(cfs_rq, se, 0);
+		place_entity(cfs_rq, se, flags);
 
 	account_entity_enqueue(cfs_rq, se);
 
@@ -12053,7 +12053,7 @@ static void task_fork_fair(struct task_s
 	curr = cfs_rq->curr;
 	if (curr)
 		update_curr(cfs_rq);
-	place_entity(cfs_rq, se, 1);
+	place_entity(cfs_rq, se, ENQUEUE_INITIAL);
 	rq_unlock(rq, &rf);
 }

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2174,6 +2174,7 @@ extern const u32		sched_prio_to_wmult[40
 #else
 #define ENQUEUE_MIGRATED	0x00
 #endif
+#define ENQUEUE_INITIAL		0x80
 
 #define RETRY_TASK		((void *)-1UL)

 /*
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -555,6 +555,7 @@ struct cfs_rq {
 	unsigned int		idle_h_nr_running; /* SCHED_IDLE */
 
 	s64			avg_vruntime;
+	u64			avg_slice;
 	u64			avg_load;
 
 	u64			exec_clock;

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -642,6 +642,7 @@ avg_vruntime_add(struct cfs_rq *cfs_rq,
 	s64 key = entity_key(cfs_rq, se);
 
 	cfs_rq->avg_vruntime += key * weight;
+	cfs_rq->avg_slice += se->slice * weight;
 	cfs_rq->avg_load += weight;
 }
 
@@ -652,6 +653,7 @@ avg_vruntime_sub(struct cfs_rq *cfs_rq,
 	s64 key = entity_key(cfs_rq, se);
 
 	cfs_rq->avg_vruntime -= key * weight;
+	cfs_rq->avg_slice -= se->slice * weight;
 	cfs_rq->avg_load -= weight;
 }

@@ -4908,6 +4910,21 @@ static inline void update_misfit_status(
 
 #endif /* CONFIG_SMP */
 
+static inline bool
+entity_has_slept(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+{
+	u64 now;
+
+	if (!(flags & ENQUEUE_WAKEUP))
+		return false;
+
+	if (flags & ENQUEUE_MIGRATED)
+		return true;
+
+	now = rq_clock_task(rq_of(cfs_rq));
+	return (s64)(se->exec_start - now) >= se->slice;
+}
+

--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -5,6 +5,7 @@
  * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled.
  */
 SCHED_FEAT(PLACE_LAG, true)
+SCHED_FEAT(PLACE_FUDGE, true)
 SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)

 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
@@ -4930,6 +4947,19 @@ place_entity(struct cfs_rq *cfs_rq, stru
 		lag = se->vlag;
 
 		/*
+		 * For latency sensitive tasks; those that have a shorter than
+		 * average slice and do not fully consume the slice, transition
+		 * to EEVDF placement strategy #2.
+		 */
+		if (sched_feat(PLACE_FUDGE) &&
+		    (cfs_rq->avg_slice > se->slice * cfs_rq->avg_load) &&
+		    entity_has_slept(cfs_rq, se, flags)) {
+			lag += vslice;
+			if (lag > 0)
+				lag = 0;
+		}
+
+		/*
 		 * If we want to place a task and preserve lag, we have to
 		 * consider the effect of the new entity on the weighted
 		 * average and compensate for this, otherwise lag can quickly

	/*
	 * VRUNTIME
	 * ========
	 *
	 * COROLLARY #1: The virtual runtime of the entity needs to be
	 * adjusted if re-weight at !0-lag point.
	 *
	 * Proof: For contradiction assume this is not true, so we can
	 * re-weight without changing vruntime at !0-lag point.
	 *
	 *             Weight	VRuntime   Avg-VRuntime
	 *     before    w          v            V
	 *      after    w'         v'           V'
	 *
	 * Since lag needs to be preserved through re-weight:
	 *
	 *	lag = (V - v)*w = (V'- v')*w', where v = v'
	 *	==>	V' = (V - v)*w/w' + v		(1)
	 *
	 * Let W be the total weight of the entities before reweight,
	 * since V' is the new weighted average of entities:
	 *
	 *	V' = (WV + w'v - wv) / (W + w' - w)	(2)
	 *
	 * by using (1) & (2) we obtain:
	 *
	 *	(WV + w'v - wv) / (W + w' - w) = (V - v)*w/w' + v
	 *	==> (WV-Wv+Wv+w'v-wv)/(W+w'-w) = (V - v)*w/w' + v
	 *	==> (WV - Wv)/(W + w' - w) + v = (V - v)*w/w' + v
	 *	==>	(V - v)*W/(W + w' - w) = (V - v)*w/w' (3)
	 *
	 * Since we are doing at !0-lag point which means V != v, we
	 * can simplify (3):
	 *
	 *	==>	W / (W + w' - w) = w / w'
	 *	==>	Ww' = Ww + ww' - ww
	 *	==>	W * (w' - w) = w * (w' - w)
	 *	==>	W = w	(re-weight indicates w' != w)
	 *
	 * So the cfs_rq contains only one entity, hence vruntime of
	 * the entity @v should always equal to the cfs_rq's weighted
	 * average vruntime @V, which means we will always re-weight
	 * at 0-lag point, thus breach assumption. Proof completed.
	 */

	/*
	 * COROLLARY #2: Re-weight does NOT affect weighted average
	 * vruntime of all the entities.
	 *
	 * Proof: According to corollary #1, Eq. (1) should be:
	 *
	 *	(V - v)*w = (V' - v')*w'
	 *	==>    v' = V' - (V - v)*w/w'		(4)
	 *
	 * According to the weighted average formula, we have:
	 *
	 *	V' = (WV - wv + w'v') / (W - w + w')
	 *	   = (WV - wv + w'(V' - (V - v)w/w')) / (W - w + w')
	 *	   = (WV - wv + w'V' - Vw + wv) / (W - w + w')
	 *	   = (WV + w'V' - Vw) / (W - w + w')
	 *
	 *	==>  V'*(W - w + w') = WV + w'V' - Vw
	 *	==>	V' * (W - w) = (W - w) * V	(5)
	 *
	 * If the entity is the only one in the cfs_rq, then reweight
	 * always occurs at 0-lag point, so V won't change. Or else
	 * there are other entities, hence W != w, then Eq. (5) turns
	 * into V' = V. So V won't change in either case, proof done.

	 /*
	 * So according to corollary #1 & #2, the effect of re-weight
	 * on vruntime should be:
	 *
	 *	v' = V' - (V - v) * w / w'		(4)
	 *	   = V  - (V - v) * w / w'
	 *	   = V  - vl * w / w'
	 *	   = V  - vl'
	 */

static void reweight_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *se,
			   unsigned long weight)
{
	unsigned long old_weight = se->load.weight;
	u64 avruntime = avg_vruntime(cfs_rq);
	s64 vlag, vslice;

	if (avruntime != se->vruntime) {
		vlag = (s64)(avruntime - se->vruntime);
		vlag = div_s64(vlag * old_weight, weight);
		se->vruntime = avruntime - vlag;
	}

	/*
	 * DEADLINE
	 * ========
	 *
	 * When the weight changes, the virtual time slope changes and
	 * we should adjust the relative virtual deadline accordingly.
	 *
	 *	d' = v' + (d - v)*w/w'
	 *	   = V' - (V - v)*w/w' + (d - v)*w/w'
	 *	   = V  - (V - v)*w/w' + (d - v)*w/w'
	 *	   = V  + (d - V)*w/w'
	 */
	vslice = (s64)(se->deadline - avruntime);
	vslice = div_s64(vslice * old_weight, weight);
	se->deadline = avruntime + vslice;
}

 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 			    unsigned long weight)
 {
-	unsigned long old_weight = se->load.weight;
+	bool curr = cfs_rq->curr == se;
 
 	if (se->on_rq) {
 		/* commit outstanding execution time */
-		if (cfs_rq->curr == se)
+		if (curr)
 			update_curr(cfs_rq);
 		else
-			avg_vruntime_sub(cfs_rq, se);
+			__dequeue_entity(cfs_rq, se);
 		update_load_sub(&cfs_rq->load, se->load.weight);
 	}
 	dequeue_load_avg(cfs_rq, se);
 
-	update_load_set(&se->load, weight);
-
 	if (!se->on_rq) {
 		/*
 		 * Because we keep se->vlag = V - v_i, while: lag_i = w_i*(V - v_i),
 		 * we need to scale se->vlag when w_i changes.
 		 */
-		se->vlag = div_s64(se->vlag * old_weight, weight);
+		se->vlag = div_s64(se->vlag * se->load.weight, weight);
 	} else {
-		s64 deadline = se->deadline - se->vruntime;
-		/*
-		 * When the weight changes, the virtual time slope changes and
-		 * we should adjust the relative virtual deadline accordingly.
-		 */
-		deadline = div_s64(deadline * old_weight, weight);
-		se->deadline = se->vruntime + deadline;
-		if (se != cfs_rq->curr)
-			min_deadline_cb_propagate(&se->run_node, NULL);
+		reweight_eevdf(cfs_rq, se, weight);
 	}
 
+	update_load_set(&se->load, weight);
+
 #ifdef CONFIG_SMP
 	do {
 		u32 divider = get_pelt_divider(&se->avg);
@@ -3712,8 +3811,17 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 	enqueue_load_avg(cfs_rq, se);
 	if (se->on_rq) {
 		update_load_add(&cfs_rq->load, se->load.weight);
-		if (cfs_rq->curr != se)
-			avg_vruntime_add(cfs_rq, se);
+		if (!curr) {
+			/*
+			 * The entity's vruntime has been adjusted, so let's check
+			 * whether the rq-wide min_vruntime needs updated too. Since
+			 * the calculations above require stable min_vruntime rather
+			 * than up-to-date one, we do the update at the end of the
+			 * reweight process.
+			 */
+			__enqueue_entity(cfs_rq, se);
+			update_min_vruntime(cfs_rq);
+		}
 	}
 }

@@ -3857,14 +3965,11 @@ static void update_cfs_group(struct sched_entity *se)
 
 #ifndef CONFIG_SMP
 	shares = READ_ONCE(gcfs_rq->tg->shares);
-
-	if (likely(se->load.weight == shares))
-		return;
 #else
-	shares   = calc_group_shares(gcfs_rq);
+	shares = calc_group_shares(gcfs_rq);
 #endif
-
-	reweight_entity(cfs_rq_of(se), se, shares);
+	if (unlikely(se->load.weight != shares))
+		reweight_entity(cfs_rq_of(se), se, shares);
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */

+++ b/include/linux/sched.h
@@ -553,7 +553,7 @@ struct sched_entity {
 	struct load_weight		load;
 	struct rb_node			run_node;
 	u64				deadline;
-	u64				min_deadline;
+	u64				min_vruntime;
 
 	struct list_head		group_node;
 	unsigned int			on_rq;

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 4580a450700e..168eecc209b4 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -628,8 +628,8 @@ static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu)
 
 void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 {
-	s64 left_vruntime = -1, min_vruntime, right_vruntime = -1, spread;
-	struct sched_entity *last, *first;
+	s64 left_vruntime = -1, min_vruntime, right_vruntime = -1, left_deadline = -1, spread;
+	struct sched_entity *last, *first, *root;
 	struct rq *rq = cpu_rq(cpu);
 	unsigned long flags;
 
@@ -644,15 +644,20 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 			SPLIT_NS(cfs_rq->exec_clock));
 
 	raw_spin_rq_lock_irqsave(rq, flags);
+	root = __pick_root_entity(cfs_rq);
+	if (root)
+		left_vruntime = root->min_vruntime;
 	first = __pick_first_entity(cfs_rq);
 	if (first)
-		left_vruntime = first->vruntime;
+		left_deadline = first->deadline;
 	last = __pick_last_entity(cfs_rq);
 	if (last)
 		right_vruntime = last->vruntime;
 	min_vruntime = cfs_rq->min_vruntime;
 	raw_spin_rq_unlock_irqrestore(rq, flags);
 
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "left_deadline",
+			SPLIT_NS(left_deadline));
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "left_vruntime",
 			SPLIT_NS(left_vruntime));
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "min_vruntime",

@@ -551,7 +542,11 @@ static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 static inline bool entity_before(const struct sched_entity *a,
 				 const struct sched_entity *b)
 {
-	return (s64)(a->vruntime - b->vruntime) < 0;
+	/*
+	 * Tiebreak on vruntime seems unnecessary since it can
+	 * hardly happen.
+	 */
+	return (s64)(a->deadline - b->deadline) < 0;
 }

@@ -720,7 +715,7 @@ static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se)
  * Note: using 'avg_vruntime() > se->vruntime' is inacurate due
  *       to the loss in precision caused by the division.
  */
-int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se)
+static int vruntime_eligible(struct cfs_rq *cfs_rq, u64 vruntime)
 {
 	struct sched_entity *curr = cfs_rq->curr;
 	s64 avg = cfs_rq->avg_vruntime;
@@ -733,16 +728,19 @@ int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se)
 		load += weight;
 	}
 
-	return avg >= entity_key(cfs_rq, se) * load;
+	return avg >= (s64)(vruntime - cfs_rq->min_vruntime) * load;
+}
+
+int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+	return vruntime_eligible(cfs_rq, se->vruntime);
 }

 		min_vruntime = vruntime;
@@ -752,9 +750,8 @@ static u64 __update_min_vruntime(struct cfs_rq *cfs_rq, u64 vruntime)
 
 static void update_min_vruntime(struct cfs_rq *cfs_rq)
 {
-	struct sched_entity *se = __pick_first_entity(cfs_rq);
+	struct sched_entity *se = __pick_root_entity(cfs_rq);
 	struct sched_entity *curr = cfs_rq->curr;
-
 	u64 vruntime = cfs_rq->min_vruntime;
 
 	if (curr) {
@@ -766,9 +763,9 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq)
 
 	if (se) {
 		if (!curr)
-			vruntime = se->vruntime;
+			vruntime = se->min_vruntime;
 		else
-			vruntime = min_vruntime(vruntime, se->vruntime);
+			vruntime = min_vruntime(vruntime, se->min_vruntime);
 	}
 
 	/* ensure we never gain time by being placed backwards. */
@@ -781,34 +778,34 @@ static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
 	return e

 	/* ensure we never gain time by being placed backwards. */
@@ -781,34 +778,34 @@ static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
 	return entity_before(__node_2_se(a), __node_2_se(b));
 }
 
-#define deadline_gt(field, lse, rse) ({ (s64)((lse)->field - (rse)->field) > 0; })
+#define vruntime_gt(field, lse, rse) ({ (s64)((lse)->field - (rse)->field) > 0; })
 
-static inline void __update_min_deadline(struct sched_entity *se, struct rb_node *node)
+static inline void __min_vruntime_update(struct sched_entity *se, struct rb_node *node)
 {
 	if (node) {
 		struct sched_entity *rse = __node_2_se(node);
-		if (deadline_gt(min_deadline, se, rse))
-			se->min_deadline = rse->min_deadline;
+		if (vruntime_gt(min_vruntime, se, rse))
+			se->min_vruntime = rse->min_vruntime;
 	}
 }
  /*
- * se->min_deadline = min(se->deadline, left->min_deadline, right->min_deadline)
+ * se->min_vruntime = min(se->vruntime, {left,right}->min_vruntime)
  */
-static inline bool min_deadline_update(struct sched_entity *se, bool exit)
+static inline bool min_vruntime_update(struct sched_entity *se, bool exit)
 {
-	u64 old_min_deadline = se->min_deadline;
+	u64 old_min_vruntime = se->min_vruntime;
 	struct rb_node *node = &se->run_node;
 
-	se->min_deadline = se->deadline;
-	__update_min_deadline(se, node->rb_right);
-	__update_min_deadline(se, node->rb_left);
+	se->min_vruntime = se->vruntime;
+	__min_vruntime_update(se, node->rb_right);
+	__min_vruntime_update(se, node->rb_left);
 
-	return se->min_deadline == old_min_deadline;
+	return se->min_vruntime == old_min_vruntime;
 }
 
-RB_DECLARE_CALLBACKS(static, min_deadline_cb, struct sched_entity,
-		     run_node, min_deadline, min_deadline_update);
+RB_DECLARE_CALLBACKS(static, min_vruntime_cb, struct sched_entity,
+		     run_node, min_vruntime, min_vruntime_update);
 

@@ -816,18 +813,28 @@ RB_DECLARE_CALLBACKS(static, min_deadline_cb, struct sched_entity,
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	avg_vruntime_add(cfs_rq, se);
-	se->min_deadline = se->deadline;
+	se->min_vruntime = se->vruntime;
 	rb_add_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
-				__entity_less, &min_deadline_cb);
+				__entity_less, &min_vruntime_cb);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
-				  &min_deadline_cb);
+				  &min_vruntime_cb);
 	avg_vruntime_sub(cfs_rq, se);
 }

+struct sched_entity *__pick_root_entity(struct cfs_rq *cfs_rq)
+{
+	struct rb_node *root = cfs_rq->tasks_timeline.rb_root.rb_node;
+
+	if (!root)
+		return NULL;
+
+	return __node_2_se(root);
+}
+

@@ -850,23 +886,28 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
  *     with the earliest virtual deadline.
  *
  * We can do this in O(log n) time due to an augmented RB-tree. The
- * tree keeps the entries sorted on service, but also functions as a
- * heap based on the deadline by keeping:
+ * tree keeps the entries sorted on deadline, but also functions as a
+ * heap based on the vruntime by keeping:
  *
- *  se->min_deadline = min(se->deadline, se->{left,right}->min_deadline)
+ *  se->min_vruntime = min(se->vruntime, se->{left,right}->min_vruntime)
  *
- * Which allows an EDF like search on (sub)trees.
+ * Which allows tree pruning through eligibility.
  */

static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 {
 	struct rb_node *node = cfs_rq->tasks_timeline.rb_root.rb_node;
 	struct sched_entity *curr = cfs_rq->curr;
 	struct sched_entity *best = NULL;


	/*
	 * We can safely skip eligibility check if there is only one entity
	 * in this cfs_rq, saving some cycles.
	 */
	if (cfs_rq->nr_running == 1)
		return curr && curr->on_rq ? curr : __node_2_se(node);
 
 	if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr)))
 		curr = NULL;

 	/*
	 * Once selected, run a task until it either becomes non-eligible or
	 * until it gets a new slice. See the HACK in set_next_entity().
	 */
 	if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline)
 		return curr;

	/* Heap search for the EEVD entity */
 	while (node) {
 		struct sched_entity *se = __node_2_se(node);
		struct rb_node *left = node->rb_left;
 
 		/*
		 * Eligible entities in left subtree are always better
		 * choices, since they have earlier deadlines.
 		 */
		if (left && vruntime_eligible(cfs_rq,
					__node_2_se(left)->min_vruntime)) {
			node = left;
 			continue;
 		}
 
 		/*
		 * The left subtree either is empty or has no eligible
		 * entity, so check the current node since it is the one
		 * with earliest deadline that might be eligible.
 		 */
		if (entity_eligible(cfs_rq, se)) {
			best = se;

 			break;

 		}
 
 		node = node->rb_right;
 	}

	if (!best || (curr && entity_before(curr, best)))
		best = curr;

	return best;
 }

@@ -896,6 +896,7 @@ int sched_update_scaling(void)
 static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 {
 	struct rb_node *node = cfs_rq->tasks_timeline.rb_root.rb_node;
+	struct sched_entity *se = __pick_first_entity(cfs_rq);
 	struct sched_entity *curr = cfs_rq->curr;
 	struct sched_entity *best = NULL;

@@ -904,7 +905,7 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 	 * in this cfs_rq, saving some cycles.
 	 */
 	if (cfs_rq->nr_running == 1)
-		return curr && curr->on_rq ? curr : __node_2_se(node);
+		return curr && curr->on_rq ? curr : se;

 	if (curr && (!curr->on_rq || !entity_eligible(cfs_rq, curr)))
 		curr = NULL;
@@ -916,9 +917,14 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 	if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline)
 		return curr;
 
+	/* Pick the leftmost entity if it's eligible */
+	if (se && entity_eligible(cfs_rq, se)) {
+		best = se;
+		goto found;
+	}
+

 	/* Heap search for the EEVD entity */
 	while (node) {
-		struct sched_entity *se = __node_2_se(node);
 		struct rb_node *left = node->rb_left;
 
 		/*
@@ -931,6 +937,8 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 			continue;
 		}
 
+		se = __node_2_se(node);
+
 		/*
 		 * The left subtree either is empty or has no eligible
 		 * entity, so check the current node since it is the one
@@ -943,7 +951,7 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 
 		node = node->rb_right;
 	}

+found:
 	if (!best || (curr && entity_before(curr, best)))
 		best = curr;

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -791,6 +791,7 @@ struct task_struct {
 	int				static_prio;
 	int				normal_prio;
 	unsigned int			rt_priority;
+	int				latency_prio;
 
 	struct sched_entity		se;
 	struct sched_rt_entity		rt;

--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -132,6 +132,7 @@ struct clone_args {
 #define SCHED_FLAG_KEEP_PARAMS		0x10
 #define SCHED_FLAG_UTIL_CLAMP_MIN	0x20
 #define SCHED_FLAG_UTIL_CLAMP_MAX	0x40
+#define SCHED_FLAG_LATENCY_NICE		0x80
 
 #define SCHED_FLAG_KEEP_ALL	(SCHED_FLAG_KEEP_POLICY | \
 				 SCHED_FLAG_KEEP_PARAMS)
@@ -143,6 +144,7 @@ struct clone_args {
 			 SCHED_FLAG_RECLAIM		| \
 			 SCHED_FLAG_DL_OVERRUN		| \
 			 SCHED_FLAG_KEEP_ALL		| \
-			 SCHED_FLAG_UTIL_CLAMP)
+			 SCHED_FLAG_UTIL_CLAMP		| \
+			 SCHED_FLAG_LATENCY_NICE)
 
 #endif /* _UAPI_LINUX_SCHED_H */

--- a/include/uapi/linux/sched/types.h
+++ b/include/uapi/linux/sched/types.h
@@ -10,6 +10,7 @@ struct sched_param {
 
 #define SCHED_ATTR_SIZE_VER0	48	/* sizeof first published struct */
 #define SCHED_ATTR_SIZE_VER1	56	/* add: util_{min,max} */
+#define SCHED_ATTR_SIZE_VER2	60	/* add: latency_nice */

 /*
  * Extended scheduling parameters data structure.
@@ -98,6 +99,22 @@ struct sched_param {
  * scheduled on a CPU with no more capacity than the specified value.
  *
  * A task utilization boundary can be reset by setting the attribute to -1.
+ *
+ * Latency Tolerance Attributes
+ * ===========================
+ *
+ * A subset of sched_attr attributes allows to specify the relative latency
+ * requirements of a task with respect to the other tasks running/queued in the
+ * system.
+ *
+ * @ sched_latency_nice	task's latency_nice value
+ *
+ * The latency_nice of a task can have any value in a range of
+ * [MIN_LATENCY_NICE..MAX_LATENCY_NICE].
+ *
+ * A task with latency_nice with the value of LATENCY_NICE_MIN can be
+ * taken for a task requiring a lower latency as opposed to the task with
+ * higher latency_nice.
  */
 struct sched_attr {
 	__u32 size;
@@ -120,6 +137,8 @@ struct sched_attr {
 	__u32 sched_util_min;
 	__u32 sched_util_max;
 
+	/* latency requirement hints */
+	__s32 sched_latency_nice;
 };
 
 #endif /* _UAPI_LINUX_SCHED_TYPES_H */

--- a/init/init_task.c
+++ b/init/init_task.c
@@ -78,6 +78,7 @@ struct task_struct init_task
 	.prio		= MAX_PRIO - 20,
 	.static_prio	= MAX_PRIO - 20,
 	.normal_prio	= MAX_PRIO - 20,
+	.latency_prio	= DEFAULT_PRIO,
 	.policy		= SCHED_NORMAL,
 	.cpus_ptr	= &init_task.cpus_mask,
 	.user_cpus_ptr	= NULL,
@@ -89,7 +90,7 @@ struct task_struct init_task
 		.fn = do_no_restart_syscall,
 	},

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4719,6 +4719,8 @@ int sched_fork(unsigned long clone_flags
 		p->prio = p->normal_prio = p->static_prio;
 		set_load_weight(p, false);
 
+		p->latency_prio = NICE_TO_PRIO(0);
+
 		/*
 		 * We don't need the reset flag anymore after the fork. It has
 		 * fulfilled its duty:

+static void __setscheduler_latency(struct task_struct *p,
+				   const struct sched_attr *attr)
+{
+	if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE)
+		p->latency_prio = NICE_TO_PRIO(attr->sched_latency_nice);
+}
+
 /*
  * Check the target process has a UID that matches the current process's:
  */
@@ -7641,6 +7650,13 @@ static int __sched_setscheduler(struct t
 			return retval;
 	}
 
+	if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE) {
+		if (attr->sched_latency_nice > MAX_NICE)
+			return -EINVAL;
+		if (attr->sched_latency_nice < MIN_NICE)
+			return -EINVAL;
+	}
+
 	if (pi)
 		cpuset_read_lock();
 
@@ -7675,6 +7691,9 @@ static int __sched_setscheduler(struct t
 			goto change;
 		if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
 			goto change;
+		if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE &&
+		    attr->sched_latency_nice != PRIO_TO_NICE(p->latency_prio))
+			goto change;
 
 		p->sched_reset_on_fork = reset_on_fork;
 		retval = 0;
@@ -7763,6 +7782,7 @@ static int __sched_setscheduler(struct t
 		__setscheduler_params(p, attr);
 		__setscheduler_prio(p, newprio);
 	}
+	__setscheduler_latency(p, attr);
 	__setscheduler_uclamp(p, attr);

 	if (queued) {
@@ -7973,6 +7993,9 @@ static int sched_copy_attr(struct sched_
 	    size < SCHED_ATTR_SIZE_VER1)
 		return -EINVAL;
 
+	if ((attr->sched_flags & SCHED_FLAG_LATENCY_NICE) &&
+	    size < SCHED_ATTR_SIZE_VER2)
+		return -EINVAL;

 	/*
 	 * XXX: Do we want to be lenient like existing syscalls; or do we want
 	 * to be strict and return an error on out-of-bounds values?
@@ -8210,6 +8233,8 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pi
 	get_params(p, &kattr);
 	kattr.sched_flags &= SCHED_FLAG_ALL;
 
+	kattr.sched_latency_nice = PRIO_TO_NICE(p->latency_prio);
+
 #ifdef CONFIG_UCLAMP_TASK
 	/*
 	 * This could race with another potential updater, but this is fine

--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1085,6 +1085,7 @@ void proc_sched_show_task(struct task_st
 #endif
 	P(policy);
 	P(prio);
+	P(latency_prio);
 	if (task_has_dl_policy(p)) {
 		P(dl.runtime);
 		P(dl.deadline);

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1305,6 +1305,12 @@ static void set_load_weight(struct task_
 	}
 }
 
+static inline void set_latency_prio(struct task_struct *p, int prio)
+{
+	p->latency_prio = prio;
+	set_latency_fair(&p->se, prio - MAX_RT_PRIO);
+}
+

 #ifdef CONFIG_UCLAMP_TASK
 /*
  * Serializes updates of utilization clamp values
@@ -4464,9 +4470,10 @@ static void __sched_fork(unsigned long c
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
 	p->se.vlag			= 0;
-	p->se.slice			= sysctl_sched_base_slice;
 	INIT_LIST_HEAD(&p->se.group_node);
 
+	set_latency_prio(p, p->latency_prio);
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	p->se.cfs_rq			= NULL;
 #endif
@@ -4718,8 +4725,7 @@ int sched_fork(unsigned long clone_flags
 
 		p->prio = p->normal_prio = p->static_prio;
 		set_load_weight(p, false);
-
-		p->latency_prio = NICE_TO_PRIO(0);
+		set_latency_prio(p, NICE_TO_PRIO(0));
 
 		/*
 		 * We don't need the reset flag anymore after the fork. It has
@@ -7507,7 +7513,7 @@ static void __setscheduler_latency(struc
 				   const struct sched_attr *attr)
 {
 	if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE)
-		p->latency_prio = NICE_TO_PRIO(attr->sched_latency_nice);
+		set_latency_prio(p, NICE_TO_PRIO(attr->sched_latency_nice));
 }

 /*
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -952,6 +952,21 @@ int sched_update_scaling(void)
 }
 #endif
 
+void set_latency_fair(struct sched_entity *se, int prio)
+{
+	u32 weight = sched_prio_to_weight[prio];
+	u64 base = sysctl_sched_base_slice;
+
+	/*
+	 * For EEVDF the virtual time slope is determined by w_i (iow.
+	 * nice) while the request time r_i is determined by
+	 * latency-nice.
+	 *
+	 * Smaller request gets better latency.
+	 */
+	se->slice = div_u64(base << SCHED_FIXEDPOINT_SHIFT, weight);
+}
+

 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
 
 /*
@@ -964,13 +979,6 @@ static void update_deadline(struct cfs_r
 		return;
 
 	/*
-	 * For EEVDF the virtual time slope is determined by w_i (iow.
-	 * nice) while the request time r_i is determined by
-	 * sysctl_sched_base_slice.
-	 */
-	se->slice = sysctl_sched_base_slice;
-
-	/*
 	 * EEVDF: vd_i = ve_i + r_i / w_i
 	 */
 	se->deadline = se->vruntime + calc_delta_fair(se->slice, se);

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2495,6 +2495,8 @@ extern unsigned int sysctl_numa_balancin
 extern unsigned int sysctl_numa_balancing_hot_threshold;
 #endif
 
+extern void set_latency_fair(struct sched_entity *se, int prio);
+
 #ifdef CONFIG_SCHED_HRTICK
 
 /*

--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1121,6 +1121,16 @@ All time durations are in microseconds.
         values similar to the sched_setattr(2). This maximum utilization
         value is used to clamp the task specific maximum utilization clamp.
 
+  cpu.latency.nice
+	A read-write single value file which exists on non-root
+	cgroups.  The default is "0".
+
+	The nice value is in the range [-20, 19].
+
+	This interface file allows reading and setting latency using the
+	same values used by sched_setattr(2). The latency_nice of a group is
+	used to limit the impact of the latency_nice of a task outside the
+	group.
+	

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -378,6 +378,8 @@ struct task_group {
 
 	/* A positive value indicates that this is a SCHED_IDLE group. */
 	int			idle;
+	/* latency priority of the group. */
+	int			latency_prio;
 
 #ifdef	CONFIG_SMP
 	/*
@@ -488,6 +490,8 @@ extern int sched_group_set_shares(struct
 
 extern int sched_group_set_idle(struct task_group *tg, long idle);
 
+extern int sched_group_set_latency(struct task_group *tg, int prio);
+

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11177,6 +11177,25 @@ static int cpu_idle_write_s64(struct cgr
 {
 	return sched_group_set_idle(css_tg(css), idle);
 }
+
+static s64 cpu_latency_nice_read_s64(struct cgroup_subsys_state *css,
+				    struct cftype *cft)
+{
+	return PRIO_TO_NICE(css_tg(css)->latency_prio);
+}
+

+static int cpu_latency_nice_write_s64(struct cgroup_subsys_state *css,
+				     struct cftype *cft, s64 nice)
+{
+	int prio;
+
+	if (nice < MIN_NICE || nice > MAX_NICE)
+		return -ERANGE;
+
+	prio = NICE_TO_PRIO(nice);
+
+	return sched_group_set_latency(css_tg(css), prio);
+}
 #endif

 static struct cftype cpu_legacy_files[] = {
@@ -11191,6 +11210,11 @@ static struct cftype cpu_legacy_files[]
 		.read_s64 = cpu_idle_read_s64,
 		.write_s64 = cpu_idle_write_s64,
 	},
+	{
+		.name = "latency.nice",
+		.read_s64 = cpu_latency_nice_read_s64,
+		.write_s64 = cpu_latency_nice_write_s64,
+	},

@@ -11408,6 +11432,12 @@ static struct cftype cpu_files[] = {
 		.read_s64 = cpu_idle_read_s64,
 		.write_s64 = cpu_idle_write_s64,
 	},
+	{
+		.name = "latency.nice",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_s64 = cpu_latency_nice_read_s64,
+		.write_s64 = cpu_latency_nice_write_s64,
+	},
 #endif
 #ifdef CONFIG_CFS_BANDWIDTH

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12293,6 +12293,7 @@ int alloc_fair_sched_group(struct task_g
 		goto err;
 
 	tg->shares = NICE_0_LOAD;
+	tg->latency_prio = DEFAULT_PRIO;
 
 	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

@@ -12391,6 +12392,9 @@ void init_tg_cfs_entry(struct task_group
 	}
 
 	se->my_q = cfs_rq;
+
+	set_latency_fair(se, tg->latency_prio - MAX_RT_PRIO);
+
 	/* guarantee group entities always have weight */
 	update_load_set(&se->load, NICE_0_LOAD);
 	se->parent = parent;
@@ -12519,6 +12523,29 @@ int sched_group_set_idle(struct task_gro
 
 	mutex_unlock(&shares_mutex);
 	return 0;

+}
+
+int sched_group_set_latency(struct task_group *tg, int prio)
+{
+	int i;
+
+	if (tg == &root_task_group)
+		return -EINVAL;
+
+	mutex_lock(&shares_mutex);
+
+	if (tg->latency_prio == prio) {
+		mutex_unlock(&shares_mutex);
+		return 0;
+	}
+
+	tg->latency_prio = prio;
+
+	for_each_possible_cpu(i)
+		set_latency_fair(tg->se[i], prio - MAX_RT_PRIO);
+
+	mutex_unlock(&shares_mutex);
+	return 0;
 }

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7494,10 +7494,18 @@ static void __setscheduler_params(struct
 
 	p->policy = policy;
 
-	if (dl_policy(policy))
+	if (dl_policy(policy)) {
 		__setparam_dl(p, attr);
-	else if (fair_policy(policy))
+	} else if (fair_policy(policy)) {
 		p->static_prio = NICE_TO_PRIO(attr->sched_nice);
+		if (attr->sched_runtime) {
+			p->se.slice = clamp_t(u64, attr->sched_runtime,
+					      NSEC_PER_MSEC/10,   /* HZ=1000 * 10 */
+					      NSEC_PER_MSEC*100); /* HZ=100  / 10 */
+		} else {
+			p->se.slice = sysctl_sched_base_slice;
+		}
+	}
 
 	/*
 	 * __sched_setscheduler() ensures attr->sched_priority == 0 when
@@ -7689,7 +7697,9 @@ static int __sched_setscheduler(struct t
 	 * but store a possible modification of reset_on_fork.
 	 */
 	if (unlikely(policy == p->policy)) {
-		if (fair_policy(policy) && attr->sched_nice != task_nice(p))
+		if (fair_policy(policy) &&
+		    (attr->sched_nice != task_nice(p) ||
+		     (attr->sched_runtime && attr->sched_runtime != p->se.slice)))
 			goto change;
 		if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
 			goto change;
@@ -8017,12 +8027,14 @@ static int sched_copy_attr(struct sched_
 
 static void get_params(struct task_struct *p, struct sched_attr *attr)
 {
-	if (task_has_dl_policy(p))
+	if (task_has_dl_policy(p)) {
 		__getparam_dl(p, attr);
-	else if (task_has_rt_policy(p))
+	} else if (task_has_rt_policy(p)) {
 		attr->sched_priority = p->rt_priority;
-	else
+	} else {
 		attr->sched_nice = task_nice(p);
+		attr->sched_runtime = p->se.slice;
+	}
 }
 
 /**