sched: cfs core, kernel/sched_fair.c

add kernel/sched_fair.c - which implements the bulk of CFS's
behavioral changes for SCHED_OTHER tasks.

see Documentation/sched-design-CFS.txt about details.

Authors:

 Ingo Molnar <mingo@elte.hu>
 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 Mike Galbraith <efault@gmx.de>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>

include/linux/sched.h

@@ -1243,6 +1243,14 @@ static inline void idle_task_exit(void) {}
 
 extern void sched_idle_next(void);
 
+extern unsigned int sysctl_sched_granularity;
+extern unsigned int sysctl_sched_wakeup_granularity;
+extern unsigned int sysctl_sched_batch_wakeup_granularity;
+extern unsigned int sysctl_sched_stat_granularity;
+extern unsigned int sysctl_sched_runtime_limit;
+extern unsigned int sysctl_sched_child_runs_first;
+extern unsigned int sysctl_sched_features;
+
 #ifdef CONFIG_RT_MUTEXES
 extern int rt_mutex_getprio(struct task_struct *p);
 extern void rt_mutex_setprio(struct task_struct *p, int prio);

kernel/sched_fair.c

@@ -0,0 +1,1131 @@
+/*
+ * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
+ *
+ *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ *  Interactivity improvements by Mike Galbraith
+ *  (C) 2007 Mike Galbraith <efault@gmx.de>
+ *
+ *  Various enhancements by Dmitry Adamushko.
+ *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
+ *
+ *  Group scheduling enhancements by Srivatsa Vaddagiri
+ *  Copyright IBM Corporation, 2007
+ *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
+ *
+ *  Scaled math optimizations by Thomas Gleixner
+ *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
+ */
+
+/*
+ * Preemption granularity:
+ * (default: 2 msec, units: nanoseconds)
+ *
+ * NOTE: this granularity value is not the same as the concept of
+ * 'timeslice length' - timeslices in CFS will typically be somewhat
+ * larger than this value. (to see the precise effective timeslice
+ * length of your workload, run vmstat and monitor the context-switches
+ * field)
+ *
+ * On SMP systems the value of this is multiplied by the log2 of the
+ * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
+ * systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
+ */
+unsigned int sysctl_sched_granularity __read_mostly = 2000000000ULL/HZ;
+
+/*
+ * SCHED_BATCH wake-up granularity.
+ * (default: 10 msec, units: nanoseconds)
+ *
+ * This option delays the preemption effects of decoupled workloads
+ * and reduces their over-scheduling. Synchronous workloads will still
+ * have immediate wakeup/sleep latencies.
+ */
+unsigned int sysctl_sched_batch_wakeup_granularity __read_mostly =
+							10000000000ULL/HZ;
+
+/*
+ * SCHED_OTHER wake-up granularity.
+ * (default: 1 msec, units: nanoseconds)
+ *
+ * This option delays the preemption effects of decoupled workloads
+ * and reduces their over-scheduling. Synchronous workloads will still
+ * have immediate wakeup/sleep latencies.
+ */
+unsigned int sysctl_sched_wakeup_granularity __read_mostly = 1000000000ULL/HZ;
+
+unsigned int sysctl_sched_stat_granularity __read_mostly;
+
+/*
+ * Initialized in sched_init_granularity():
+ */
+unsigned int sysctl_sched_runtime_limit __read_mostly;
+
+/*
+ * Debugging: various feature bits
+ */
+enum {
+	SCHED_FEAT_FAIR_SLEEPERS	= 1,
+	SCHED_FEAT_SLEEPER_AVG		= 2,
+	SCHED_FEAT_SLEEPER_LOAD_AVG	= 4,
+	SCHED_FEAT_PRECISE_CPU_LOAD	= 8,
+	SCHED_FEAT_START_DEBIT		= 16,
+	SCHED_FEAT_SKIP_INITIAL		= 32,
+};
+
+unsigned int sysctl_sched_features __read_mostly =
+		SCHED_FEAT_FAIR_SLEEPERS	*1 |
+		SCHED_FEAT_SLEEPER_AVG		*1 |
+		SCHED_FEAT_SLEEPER_LOAD_AVG	*1 |
+		SCHED_FEAT_PRECISE_CPU_LOAD	*1 |
+		SCHED_FEAT_START_DEBIT		*1 |
+		SCHED_FEAT_SKIP_INITIAL		*0;
+
+extern struct sched_class fair_sched_class;
+
+/**************************************************************
+ * CFS operations on generic schedulable entities:
+ */
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+/* cpu runqueue to which this cfs_rq is attached */
+static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
+{
+	return cfs_rq->rq;
+}
+
+/* currently running entity (if any) on this cfs_rq */
+static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
+{
+	return cfs_rq->curr;
+}
+
+/* An entity is a task if it doesn't "own" a runqueue */
+#define entity_is_task(se)	(!se->my_q)
+
+static inline void
+set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+	cfs_rq->curr = se;
+}
+
+#else	/* CONFIG_FAIR_GROUP_SCHED */
+
+static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
+{
+	return container_of(cfs_rq, struct rq, cfs);
+}
+
+static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
+{
+	struct rq *rq = rq_of(cfs_rq);
+
+	if (unlikely(rq->curr->sched_class != &fair_sched_class))
+		return NULL;
+
+	return &rq->curr->se;
+}
+
+#define entity_is_task(se)	1
+
+static inline void
+set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
+
+#endif	/* CONFIG_FAIR_GROUP_SCHED */
+
+static inline struct task_struct *task_of(struct sched_entity *se)
+{
+	return container_of(se, struct task_struct, se);
+}
+
+
+/**************************************************************
+ * Scheduling class tree data structure manipulation methods:
+ */
+
+/*
+ * Enqueue an entity into the rb-tree:
+ */
+static inline void
+__enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
+	struct rb_node *parent = NULL;
+	struct sched_entity *entry;
+	s64 key = se->fair_key;
+	int leftmost = 1;
+
+	/*
+	 * Find the right place in the rbtree:
+	 */
+	while (*link) {
+		parent = *link;
+		entry = rb_entry(parent, struct sched_entity, run_node);
+		/*
+		 * We dont care about collisions. Nodes with
+		 * the same key stay together.
+		 */
+		if (key - entry->fair_key < 0) {
+			link = &parent->rb_left;
+		} else {
+			link = &parent->rb_right;
+			leftmost = 0;
+		}
+	}
+
+	/*
+	 * Maintain a cache of leftmost tree entries (it is frequently
+	 * used):
+	 */
+	if (leftmost)
+		cfs_rq->rb_leftmost = &se->run_node;
+
+	rb_link_node(&se->run_node, parent, link);
+	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
+	update_load_add(&cfs_rq->load, se->load.weight);
+	cfs_rq->nr_running++;
+	se->on_rq = 1;
+}
+
+static inline void
+__dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+	if (cfs_rq->rb_leftmost == &se->run_node)
+		cfs_rq->rb_leftmost = rb_next(&se->run_node);
+	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
+	update_load_sub(&cfs_rq->load, se->load.weight);
+	cfs_rq->nr_running--;
+	se->on_rq = 0;
+}
+
+static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
+{
+	return cfs_rq->rb_leftmost;
+}
+
+static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
+{
+	return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
+}
+
+/**************************************************************
+ * Scheduling class statistics methods:
+ */
+
+/*
+ * We rescale the rescheduling granularity of tasks according to their
+ * nice level, but only linearly, not exponentially:
+ */
+static long
+niced_granularity(struct sched_entity *curr, unsigned long granularity)
+{
+	u64 tmp;
+
+	/*
+	 * Negative nice levels get the same granularity as nice-0:
+	 */
+	if (likely(curr->load.weight >= NICE_0_LOAD))
+		return granularity;
+	/*
+	 * Positive nice level tasks get linearly finer
+	 * granularity:
+	 */
+	tmp = curr->load.weight * (u64)granularity;
+
+	/*
+	 * It will always fit into 'long':
+	 */
+	return (long) (tmp >> NICE_0_SHIFT);
+}
+
+static inline void
+limit_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+	long limit = sysctl_sched_runtime_limit;
+
+	/*
+	 * Niced tasks have the same history dynamic range as
+	 * non-niced tasks:
+	 */
+	if (unlikely(se->wait_runtime > limit)) {
+		se->wait_runtime = limit;
+		schedstat_inc(se, wait_runtime_overruns);
+		schedstat_inc(cfs_rq, wait_runtime_overruns);
+	}
+	if (unlikely(se->wait_runtime < -limit)) {
+		se->wait_runtime = -limit;
+		schedstat_inc(se, wait_runtime_underruns);
+		schedstat_inc(cfs_rq, wait_runtime_underruns);
+	}
+}
+
+static inline void
+__add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
+{
+	se->wait_runtime += delta;
+	schedstat_add(se, sum_wait_runtime, delta);
+	limit_wait_runtime(cfs_rq, se);
+}
+
+static void
+add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
+{
+	schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime);
+	__add_wait_runtime(cfs_rq, se, delta);
+	schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
+}
+
+/*
+ * Update the current task's runtime statistics. Skip current tasks that
+ * are not in our scheduling class.
+ */
+static inline void
+__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr, u64 now)
+{
+	unsigned long delta, delta_exec, delta_fair;
+	long delta_mine;
+	struct load_weight *lw = &cfs_rq->load;
+	unsigned long load = lw->weight;
+
+	if (unlikely(!load))
+		return;
+
+	delta_exec = curr->delta_exec;
+#ifdef CONFIG_SCHEDSTATS
+	if (unlikely(delta_exec > curr->exec_max))
+		curr->exec_max = delta_exec;
+#endif
+
+	curr->sum_exec_runtime += delta_exec;
+	cfs_rq->exec_clock += delta_exec;
+
+	delta_fair = calc_delta_fair(delta_exec, lw);
+	delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
+
+	if (cfs_rq->sleeper_bonus > sysctl_sched_stat_granularity) {
+		delta = calc_delta_mine(cfs_rq->sleeper_bonus,
+					curr->load.weight, lw);
+		if (unlikely(delta > cfs_rq->sleeper_bonus))
+			delta = cfs_rq->sleeper_bonus;
+
+		cfs_rq->sleeper_bonus -= delta;
+		delta_mine -= delta;
+	}
+
+	cfs_rq->fair_clock += delta_fair;
+	/*
+	 * We executed delta_exec amount of time on the CPU,
+	 * but we were only entitled to delta_mine amount of
+	 * time during that period (if nr_running == 1 then
+	 * the two values are equal)
+	 * [Note: delta_mine - delta_exec is negative]:
+	 */
+	add_wait_runtime(cfs_rq, curr, delta_mine - delta_exec);
+}
+
+static void update_curr(struct cfs_rq *cfs_rq, u64 now)
+{
+	struct sched_entity *curr = cfs_rq_curr(cfs_rq);
+	unsigned long delta_exec;
+
+	if (unlikely(!curr))
+		return;
+
+	/*
+	 * Get the amount of time the current task was running
+	 * since the last time we changed load (this cannot
+	 * overflow on 32 bits):
+	 */
+	delta_exec = (unsigned long)(now - curr->exec_start);
+
+	curr->delta_exec += delta_exec;
+
+	if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) {
+		__update_curr(cfs_rq, curr, now);
+		curr->delta_exec = 0;
+	}
+	curr->exec_start = now;
+}
+
+static inline void
+update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	se->wait_start_fair = cfs_rq->fair_clock;
+	se->wait_start = now;
+}
+
+/*
+ * We calculate fair deltas here, so protect against the random effects
+ * of a multiplication overflow by capping it to the runtime limit:
+ */
+#if BITS_PER_LONG == 32
+static inline unsigned long
+calc_weighted(unsigned long delta, unsigned long weight, int shift)
+{
+	u64 tmp = (u64)delta * weight >> shift;
+
+	if (unlikely(tmp > sysctl_sched_runtime_limit*2))
+		return sysctl_sched_runtime_limit*2;
+	return tmp;
+}
+#else
+static inline unsigned long
+calc_weighted(unsigned long delta, unsigned long weight, int shift)
+{
+	return delta * weight >> shift;
+}
+#endif
+
+/*
+ * Task is being enqueued - update stats:
+ */
+static void
+update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	s64 key;
+
+	/*
+	 * Are we enqueueing a waiting task? (for current tasks
+	 * a dequeue/enqueue event is a NOP)
+	 */
+	if (se != cfs_rq_curr(cfs_rq))
+		update_stats_wait_start(cfs_rq, se, now);
+	/*
+	 * Update the key:
+	 */
+	key = cfs_rq->fair_clock;
+
+	/*
+	 * Optimize the common nice 0 case:
+	 */
+	if (likely(se->load.weight == NICE_0_LOAD)) {
+		key -= se->wait_runtime;
+	} else {
+		u64 tmp;
+
+		if (se->wait_runtime < 0) {
+			tmp = -se->wait_runtime;
+			key += (tmp * se->load.inv_weight) >>
+					(WMULT_SHIFT - NICE_0_SHIFT);
+		} else {
+			tmp = se->wait_runtime;
+			key -= (tmp * se->load.weight) >> NICE_0_SHIFT;
+		}
+	}
+
+	se->fair_key = key;
+}
+
+/*
+ * Note: must be called with a freshly updated rq->fair_clock.
+ */
+static inline void
+__update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	unsigned long delta_fair = se->delta_fair_run;
+
+#ifdef CONFIG_SCHEDSTATS
+	{
+		s64 delta_wait = now - se->wait_start;
+		if (unlikely(delta_wait > se->wait_max))
+			se->wait_max = delta_wait;
+	}
+#endif
+
+	if (unlikely(se->load.weight != NICE_0_LOAD))
+		delta_fair = calc_weighted(delta_fair, se->load.weight,
+							NICE_0_SHIFT);
+
+	add_wait_runtime(cfs_rq, se, delta_fair);
+}
+
+static void
+update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	unsigned long delta_fair;
+
+	delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
+			(u64)(cfs_rq->fair_clock - se->wait_start_fair));
+
+	se->delta_fair_run += delta_fair;
+	if (unlikely(abs(se->delta_fair_run) >=
+				sysctl_sched_stat_granularity)) {
+		__update_stats_wait_end(cfs_rq, se, now);
+		se->delta_fair_run = 0;
+	}
+
+	se->wait_start_fair = 0;
+	se->wait_start = 0;
+}
+
+static inline void
+update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	update_curr(cfs_rq, now);
+	/*
+	 * Mark the end of the wait period if dequeueing a
+	 * waiting task:
+	 */
+	if (se != cfs_rq_curr(cfs_rq))
+		update_stats_wait_end(cfs_rq, se, now);
+}
+
+/*
+ * We are picking a new current task - update its stats:
+ */
+static inline void
+update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	/*
+	 * We are starting a new run period:
+	 */
+	se->exec_start = now;
+}
+
+/*
+ * We are descheduling a task - update its stats:
+ */
+static inline void
+update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	se->exec_start = 0;
+}
+
+/**************************************************
+ * Scheduling class queueing methods:
+ */
+
+static void
+__enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	unsigned long load = cfs_rq->load.weight, delta_fair;
+	long prev_runtime;
+
+	if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG)
+		load = rq_of(cfs_rq)->cpu_load[2];
+
+	delta_fair = se->delta_fair_sleep;
+
+	/*
+	 * Fix up delta_fair with the effect of us running
+	 * during the whole sleep period:
+	 */
+	if (sysctl_sched_features & SCHED_FEAT_SLEEPER_AVG)
+		delta_fair = div64_likely32((u64)delta_fair * load,
+						load + se->load.weight);
+
+	if (unlikely(se->load.weight != NICE_0_LOAD))
+		delta_fair = calc_weighted(delta_fair, se->load.weight,
+							NICE_0_SHIFT);
+
+	prev_runtime = se->wait_runtime;
+	__add_wait_runtime(cfs_rq, se, delta_fair);
+	delta_fair = se->wait_runtime - prev_runtime;
+
+	/*
+	 * Track the amount of bonus we've given to sleepers:
+	 */
+	cfs_rq->sleeper_bonus += delta_fair;
+
+	schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
+}
+
+static void
+enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	struct task_struct *tsk = task_of(se);
+	unsigned long delta_fair;
+
+	if ((entity_is_task(se) && tsk->policy == SCHED_BATCH) ||
+			 !(sysctl_sched_features & SCHED_FEAT_FAIR_SLEEPERS))
+		return;
+
+	delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
+		(u64)(cfs_rq->fair_clock - se->sleep_start_fair));
+
+	se->delta_fair_sleep += delta_fair;
+	if (unlikely(abs(se->delta_fair_sleep) >=
+				sysctl_sched_stat_granularity)) {
+		__enqueue_sleeper(cfs_rq, se, now);
+		se->delta_fair_sleep = 0;
+	}
+
+	se->sleep_start_fair = 0;
+
+#ifdef CONFIG_SCHEDSTATS
+	if (se->sleep_start) {
+		u64 delta = now - se->sleep_start;
+
+		if ((s64)delta < 0)
+			delta = 0;
+
+		if (unlikely(delta > se->sleep_max))
+			se->sleep_max = delta;
+
+		se->sleep_start = 0;
+		se->sum_sleep_runtime += delta;
+	}
+	if (se->block_start) {
+		u64 delta = now - se->block_start;
+
+		if ((s64)delta < 0)
+			delta = 0;
+
+		if (unlikely(delta > se->block_max))
+			se->block_max = delta;
+
+		se->block_start = 0;
+		se->sum_sleep_runtime += delta;
+	}
+#endif
+}
+
+static void
+enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
+	       int wakeup, u64 now)
+{
+	/*
+	 * Update the fair clock.
+	 */
+	update_curr(cfs_rq, now);
+
+	if (wakeup)
+		enqueue_sleeper(cfs_rq, se, now);
+
+	update_stats_enqueue(cfs_rq, se, now);
+	__enqueue_entity(cfs_rq, se);
+}
+
+static void
+dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
+	       int sleep, u64 now)
+{
+	update_stats_dequeue(cfs_rq, se, now);
+	if (sleep) {
+		se->sleep_start_fair = cfs_rq->fair_clock;
+#ifdef CONFIG_SCHEDSTATS
+		if (entity_is_task(se)) {
+			struct task_struct *tsk = task_of(se);
+
+			if (tsk->state & TASK_INTERRUPTIBLE)
+				se->sleep_start = now;
+			if (tsk->state & TASK_UNINTERRUPTIBLE)
+				se->block_start = now;
+		}
+		cfs_rq->wait_runtime -= se->wait_runtime;
+#endif
+	}
+	__dequeue_entity(cfs_rq, se);
+}
+
+/*
+ * Preempt the current task with a newly woken task if needed:
+ */
+static void
+__check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
+			  struct sched_entity *curr, unsigned long granularity)
+{
+	s64 __delta = curr->fair_key - se->fair_key;
+
+	/*
+	 * Take scheduling granularity into account - do not
+	 * preempt the current task unless the best task has
+	 * a larger than sched_granularity fairness advantage:
+	 */
+	if (__delta > niced_granularity(curr, granularity))
+		resched_task(rq_of(cfs_rq)->curr);
+}
+
+static inline void
+set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
+{
+	/*
+	 * Any task has to be enqueued before it get to execute on
+	 * a CPU. So account for the time it spent waiting on the
+	 * runqueue. (note, here we rely on pick_next_task() having
+	 * done a put_prev_task_fair() shortly before this, which
+	 * updated rq->fair_clock - used by update_stats_wait_end())
+	 */
+	update_stats_wait_end(cfs_rq, se, now);
+	update_stats_curr_start(cfs_rq, se, now);
+	set_cfs_rq_curr(cfs_rq, se);
+}
+
+static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq, u64 now)
+{
+	struct sched_entity *se = __pick_next_entity(cfs_rq);
+
+	set_next_entity(cfs_rq, se, now);
+
+	return se;
+}
+
+static void
+put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev, u64 now)
+{
+	/*
+	 * If still on the runqueue then deactivate_task()
+	 * was not called and update_curr() has to be done:
+	 */
+	if (prev->on_rq)
+		update_curr(cfs_rq, now);
+
+	update_stats_curr_end(cfs_rq, prev, now);
+
+	if (prev->on_rq)
+		update_stats_wait_start(cfs_rq, prev, now);
+	set_cfs_rq_curr(cfs_rq, NULL);
+}
+
+static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
+{
+	struct rq *rq = rq_of(cfs_rq);
+	struct sched_entity *next;
+	u64 now = __rq_clock(rq);
+
+	/*
+	 * Dequeue and enqueue the task to update its
+	 * position within the tree:
+	 */
+	dequeue_entity(cfs_rq, curr, 0, now);
+	enqueue_entity(cfs_rq, curr, 0, now);
+
+	/*
+	 * Reschedule if another task tops the current one.
+	 */
+	next = __pick_next_entity(cfs_rq);
+	if (next == curr)
+		return;
+
+	__check_preempt_curr_fair(cfs_rq, next, curr, sysctl_sched_granularity);
+}
+
+/**************************************************
+ * CFS operations on tasks:
+ */
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+/* Walk up scheduling entities hierarchy */
+#define for_each_sched_entity(se) \
+		for (; se; se = se->parent)
+
+static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
+{
+	return p->se.cfs_rq;
+}
+
+/* runqueue on which this entity is (to be) queued */
+static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
+{
+	return se->cfs_rq;
+}
+
+/* runqueue "owned" by this group */
+static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
+{
+	return grp->my_q;
+}
+
+/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
+ * another cpu ('this_cpu')
+ */
+static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
+{
+	/* A later patch will take group into account */
+	return &cpu_rq(this_cpu)->cfs;
+}
+
+/* Iterate thr' all leaf cfs_rq's on a runqueue */
+#define for_each_leaf_cfs_rq(rq, cfs_rq) \
+	list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
+
+/* Do the two (enqueued) tasks belong to the same group ? */
+static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
+{
+	if (curr->se.cfs_rq == p->se.cfs_rq)
+		return 1;
+
+	return 0;
+}
+
+#else	/* CONFIG_FAIR_GROUP_SCHED */
+
+#define for_each_sched_entity(se) \
+		for (; se; se = NULL)
+
+static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
+{
+	return &task_rq(p)->cfs;
+}
+
+static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
+{
+	struct task_struct *p = task_of(se);
+	struct rq *rq = task_rq(p);
+
+	return &rq->cfs;
+}
+
+/* runqueue "owned" by this group */
+static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
+{
+	return NULL;
+}
+
+static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
+{
+	return &cpu_rq(this_cpu)->cfs;
+}
+
+#define for_each_leaf_cfs_rq(rq, cfs_rq) \
+		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
+
+static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
+{
+	return 1;
+}
+
+#endif	/* CONFIG_FAIR_GROUP_SCHED */
+
+/*
+ * The enqueue_task method is called before nr_running is
+ * increased. Here we update the fair scheduling stats and
+ * then put the task into the rbtree:
+ */
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, u64 now)
+{
+	struct cfs_rq *cfs_rq;
+	struct sched_entity *se = &p->se;
+
+	for_each_sched_entity(se) {
+		if (se->on_rq)
+			break;
+		cfs_rq = cfs_rq_of(se);
+		enqueue_entity(cfs_rq, se, wakeup, now);
+	}
+}
+
+/*
+ * The dequeue_task method is called before nr_running is
+ * decreased. We remove the task from the rbtree and
+ * update the fair scheduling stats:
+ */
+static void
+dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep, u64 now)
+{
+	struct cfs_rq *cfs_rq;
+	struct sched_entity *se = &p->se;
+
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+		dequeue_entity(cfs_rq, se, sleep, now);
+		/* Don't dequeue parent if it has other entities besides us */
+		if (cfs_rq->load.weight)
+			break;
+	}
+}
+
+/*
+ * sched_yield() support is very simple - we dequeue and enqueue
+ */
+static void yield_task_fair(struct rq *rq, struct task_struct *p)
+{
+	struct cfs_rq *cfs_rq = task_cfs_rq(p);
+	u64 now = __rq_clock(rq);
+
+	/*
+	 * Dequeue and enqueue the task to update its
+	 * position within the tree:
+	 */
+	dequeue_entity(cfs_rq, &p->se, 0, now);
+	enqueue_entity(cfs_rq, &p->se, 0, now);
+}
+
+/*
+ * Preempt the current task with a newly woken task if needed:
+ */
+static void check_preempt_curr_fair(struct rq *rq, struct task_struct *p)
+{
+	struct task_struct *curr = rq->curr;
+	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+	unsigned long gran;
+
+	if (unlikely(rt_prio(p->prio))) {
+		update_curr(cfs_rq, rq_clock(rq));
+		resched_task(curr);
+		return;
+	}
+
+	gran = sysctl_sched_wakeup_granularity;
+	/*
+	 * Batch tasks prefer throughput over latency:
+	 */
+	if (unlikely(p->policy == SCHED_BATCH))
+		gran = sysctl_sched_batch_wakeup_granularity;
+
+	if (is_same_group(curr, p))
+		__check_preempt_curr_fair(cfs_rq, &p->se, &curr->se, gran);
+}
+
+static struct task_struct *pick_next_task_fair(struct rq *rq, u64 now)
+{
+	struct cfs_rq *cfs_rq = &rq->cfs;
+	struct sched_entity *se;
+
+	if (unlikely(!cfs_rq->nr_running))
+		return NULL;
+
+	do {
+		se = pick_next_entity(cfs_rq, now);
+		cfs_rq = group_cfs_rq(se);
+	} while (cfs_rq);
+
+	return task_of(se);
+}
+
+/*
+ * Account for a descheduled task:
+ */
+static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, u64 now)
+{
+	struct sched_entity *se = &prev->se;
+	struct cfs_rq *cfs_rq;
+
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+		put_prev_entity(cfs_rq, se, now);
+	}
+}
+
+/**************************************************
+ * Fair scheduling class load-balancing methods:
+ */
+
+/*
+ * Load-balancing iterator. Note: while the runqueue stays locked
+ * during the whole iteration, the current task might be
+ * dequeued so the iterator has to be dequeue-safe. Here we
+ * achieve that by always pre-iterating before returning
+ * the current task:
+ */
+static inline struct task_struct *
+__load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
+{
+	struct task_struct *p;
+
+	if (!curr)
+		return NULL;
+
+	p = rb_entry(curr, struct task_struct, se.run_node);
+	cfs_rq->rb_load_balance_curr = rb_next(curr);
+
+	return p;
+}
+
+static struct task_struct *load_balance_start_fair(void *arg)
+{
+	struct cfs_rq *cfs_rq = arg;
+
+	return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
+}
+
+static struct task_struct *load_balance_next_fair(void *arg)
+{
+	struct cfs_rq *cfs_rq = arg;
+
+	return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
+}
+
+static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
+{
+	struct sched_entity *curr;
+	struct task_struct *p;
+
+	if (!cfs_rq->nr_running)
+		return MAX_PRIO;
+
+	curr = __pick_next_entity(cfs_rq);
+	p = task_of(curr);
+
+	return p->prio;
+}
+
+static int
+load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
+			unsigned long max_nr_move, unsigned long max_load_move,
+			struct sched_domain *sd, enum cpu_idle_type idle,
+			int *all_pinned, unsigned long *total_load_moved)
+{
+	struct cfs_rq *busy_cfs_rq;
+	unsigned long load_moved, total_nr_moved = 0, nr_moved;
+	long rem_load_move = max_load_move;
+	struct rq_iterator cfs_rq_iterator;
+
+	cfs_rq_iterator.start = load_balance_start_fair;
+	cfs_rq_iterator.next = load_balance_next_fair;
+
+	for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
+		struct cfs_rq *this_cfs_rq;
+		long imbalance;
+		unsigned long maxload;
+		int this_best_prio, best_prio, best_prio_seen = 0;
+
+		this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
+
+		imbalance = busy_cfs_rq->load.weight -
+						 this_cfs_rq->load.weight;
+		/* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
+		if (imbalance <= 0)
+			continue;
+
+		/* Don't pull more than imbalance/2 */
+		imbalance /= 2;
+		maxload = min(rem_load_move, imbalance);
+
+		this_best_prio = cfs_rq_best_prio(this_cfs_rq);
+		best_prio = cfs_rq_best_prio(busy_cfs_rq);
+
+		/*
+		 * Enable handling of the case where there is more than one task
+		 * with the best priority. If the current running task is one
+		 * of those with prio==best_prio we know it won't be moved
+		 * and therefore it's safe to override the skip (based on load)
+		 * of any task we find with that prio.
+		 */
+		if (cfs_rq_curr(busy_cfs_rq) == &busiest->curr->se)
+			best_prio_seen = 1;
+
+		/* pass busy_cfs_rq argument into
+		 * load_balance_[start|next]_fair iterators
+		 */
+		cfs_rq_iterator.arg = busy_cfs_rq;
+		nr_moved = balance_tasks(this_rq, this_cpu, busiest,
+				max_nr_move, maxload, sd, idle, all_pinned,
+				&load_moved, this_best_prio, best_prio,
+				best_prio_seen, &cfs_rq_iterator);
+
+		total_nr_moved += nr_moved;
+		max_nr_move -= nr_moved;
+		rem_load_move -= load_moved;
+
+		if (max_nr_move <= 0 || rem_load_move <= 0)
+			break;
+	}
+
+	*total_load_moved = max_load_move - rem_load_move;
+
+	return total_nr_moved;
+}
+
+/*
+ * scheduler tick hitting a task of our scheduling class:
+ */
+static void task_tick_fair(struct rq *rq, struct task_struct *curr)
+{
+	struct cfs_rq *cfs_rq;
+	struct sched_entity *se = &curr->se;
+
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+		entity_tick(cfs_rq, se);
+	}
+}
+
+/*
+ * Share the fairness runtime between parent and child, thus the
+ * total amount of pressure for CPU stays equal - new tasks
+ * get a chance to run but frequent forkers are not allowed to
+ * monopolize the CPU. Note: the parent runqueue is locked,
+ * the child is not running yet.
+ */
+static void task_new_fair(struct rq *rq, struct task_struct *p)
+{
+	struct cfs_rq *cfs_rq = task_cfs_rq(p);
+	struct sched_entity *se = &p->se;
+	u64 now = rq_clock(rq);
+
+	sched_info_queued(p);
+
+	update_stats_enqueue(cfs_rq, se, now);
+	/*
+	 * Child runs first: we let it run before the parent
+	 * until it reschedules once. We set up the key so that
+	 * it will preempt the parent:
+	 */
+	p->se.fair_key = current->se.fair_key -
+		niced_granularity(&rq->curr->se, sysctl_sched_granularity) - 1;
+	/*
+	 * The first wait is dominated by the child-runs-first logic,
+	 * so do not credit it with that waiting time yet:
+	 */
+	if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL)
+		p->se.wait_start_fair = 0;
+
+	/*
+	 * The statistical average of wait_runtime is about
+	 * -granularity/2, so initialize the task with that:
+	 */
+	if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
+		p->se.wait_runtime = -(sysctl_sched_granularity / 2);
+
+	__enqueue_entity(cfs_rq, se);
+	inc_nr_running(p, rq, now);
+}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+/* Account for a task changing its policy or group.
+ *
+ * This routine is mostly called to set cfs_rq->curr field when a task
+ * migrates between groups/classes.
+ */
+static void set_curr_task_fair(struct rq *rq)
+{
+	struct task_struct *curr = rq->curr;
+	struct sched_entity *se = &curr->se;
+	u64 now = rq_clock(rq);
+	struct cfs_rq *cfs_rq;
+
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+		set_next_entity(cfs_rq, se, now);
+	}
+}
+#else
+static void set_curr_task_fair(struct rq *rq)
+{
+}
+#endif
+
+/*
+ * All the scheduling class methods:
+ */
+struct sched_class fair_sched_class __read_mostly = {
+	.enqueue_task		= enqueue_task_fair,
+	.dequeue_task		= dequeue_task_fair,
+	.yield_task		= yield_task_fair,
+
+	.check_preempt_curr	= check_preempt_curr_fair,
+
+	.pick_next_task		= pick_next_task_fair,
+	.put_prev_task		= put_prev_task_fair,
+
+	.load_balance		= load_balance_fair,
+
+	.set_curr_task          = set_curr_task_fair,
+	.task_tick		= task_tick_fair,
+	.task_new		= task_new_fair,
+};
+
+#ifdef CONFIG_SCHED_DEBUG
+void print_cfs_stats(struct seq_file *m, int cpu, u64 now)
+{
+	struct rq *rq = cpu_rq(cpu);
+	struct cfs_rq *cfs_rq;
+
+	for_each_leaf_cfs_rq(rq, cfs_rq)
+		print_cfs_rq(m, cpu, cfs_rq, now);
+}
+#endif