/*
   * 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>

   *
   *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
   *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>

   */
  
  /*

   * Targeted preemption latency for CPU-bound tasks:

   * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)

   *

   * 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)

   */

  unsigned int sysctl_sched_latency = 20000000ULL;

  
  /*

   * Minimal preemption granularity for CPU-bound tasks:

   * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)

   */

  unsigned int sysctl_sched_min_granularity = 4000000ULL;

  
  /*

   * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
   */

  static unsigned int sched_nr_latency = 5;

  
  /*
   * After fork, child runs first. (default) If set to 0 then
   * parent will (try to) run first.

   */

  const_debug unsigned int sysctl_sched_child_runs_first = 1;

  
  /*

   * sys_sched_yield() compat mode
   *
   * This option switches the agressive yield implementation of the
   * old scheduler back on.
   */
  unsigned int __read_mostly sysctl_sched_compat_yield;
  
  /*

   * SCHED_BATCH wake-up granularity.

   * (default: 10 msec * (1 + ilog(ncpus)), 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 = 10000000UL;

  
  /*
   * SCHED_OTHER wake-up granularity.

   * (default: 10 msec * (1 + ilog(ncpus)), 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 = 10000000UL;

  const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

  /**************************************************************
   * 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;

  }

  /* An entity is a task if it doesn't "own" a runqueue */
  #define entity_is_task(se)	(!se->my_q)

  #else	/* CONFIG_FAIR_GROUP_SCHED */

  static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
  {
  	return container_of(cfs_rq, struct rq, cfs);

  }
  
  #define entity_is_task(se)	1

  #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:
   */

  static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)

  {

  	s64 delta = (s64)(vruntime - min_vruntime);
  	if (delta > 0)

  		min_vruntime = vruntime;
  
  	return min_vruntime;
  }

  static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)

  {
  	s64 delta = (s64)(vruntime - min_vruntime);
  	if (delta < 0)
  		min_vruntime = vruntime;
  
  	return min_vruntime;
  }

  static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	return se->vruntime - cfs_rq->min_vruntime;

  }

  /*
   * Enqueue an entity into the rb-tree:
   */

  static 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 = entity_key(cfs_rq, se);

  	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 < entity_key(cfs_rq, entry)) {

  			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);

  }

  static 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);

  }
  
  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);
  }

  static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
  {
  	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
  	struct sched_entity *se = NULL;
  	struct rb_node *parent;
  
  	while (*link) {
  		parent = *link;
  		se = rb_entry(parent, struct sched_entity, run_node);
  		link = &parent->rb_right;
  	}
  
  	return se;
  }

  /**************************************************************
   * Scheduling class statistics methods:
   */

  #ifdef CONFIG_SCHED_DEBUG
  int sched_nr_latency_handler(struct ctl_table *table, int write,
  		struct file *filp, void __user *buffer, size_t *lenp,
  		loff_t *ppos)
  {
  	int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
  
  	if (ret || !write)
  		return ret;
  
  	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
  					sysctl_sched_min_granularity);
  
  	return 0;
  }
  #endif

  
  /*
   * The idea is to set a period in which each task runs once.
   *
   * When there are too many tasks (sysctl_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)
  {
  	u64 period = sysctl_sched_latency;

  	unsigned long nr_latency = sched_nr_latency;

  
  	if (unlikely(nr_running > nr_latency)) {
  		period *= nr_running;
  		do_div(period, nr_latency);
  	}
  
  	return period;
  }

  /*
   * We calculate the wall-time slice from the period by taking a part
   * proportional to the weight.
   *
   * s = p*w/rw
   */

  static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	u64 slice = __sched_period(cfs_rq->nr_running);

  	slice *= se->load.weight;
  	do_div(slice, cfs_rq->load.weight);

  	return slice;

  }

  /*
   * We calculate the vruntime slice.
   *
   * vs = s/w = p/rw
   */
  static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)

  {

  	u64 vslice = __sched_period(nr_running);

  	vslice *= NICE_0_LOAD;

  	do_div(vslice, rq_weight);

  	return vslice;
  }

  static u64 sched_vslice(struct cfs_rq *cfs_rq)
  {
  	return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running);
  }
  
  static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
  {
  	return __sched_vslice(cfs_rq->load.weight + se->load.weight,
  			cfs_rq->nr_running + 1);

  }

  /*
   * 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,
  	      unsigned long delta_exec)

  {

  	unsigned long delta_exec_weighted;

  	u64 vruntime;

  	schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));

  
  	curr->sum_exec_runtime += delta_exec;

  	schedstat_add(cfs_rq, exec_clock, delta_exec);

  	delta_exec_weighted = delta_exec;
  	if (unlikely(curr->load.weight != NICE_0_LOAD)) {
  		delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
  							&curr->load);
  	}
  	curr->vruntime += delta_exec_weighted;

  
  	/*
  	 * maintain cfs_rq->min_vruntime to be a monotonic increasing
  	 * value tracking the leftmost vruntime in the tree.
  	 */
  	if (first_fair(cfs_rq)) {

  		vruntime = min_vruntime(curr->vruntime,
  				__pick_next_entity(cfs_rq)->vruntime);

  	} else

  		vruntime = curr->vruntime;

  
  	cfs_rq->min_vruntime =

  		max_vruntime(cfs_rq->min_vruntime, vruntime);

  }

  static void update_curr(struct cfs_rq *cfs_rq)

  {

  	struct sched_entity *curr = cfs_rq->curr;

  	u64 now = rq_of(cfs_rq)->clock;

  	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);

  	__update_curr(cfs_rq, curr, delta_exec);
  	curr->exec_start = now;

  
  	if (entity_is_task(curr)) {
  		struct task_struct *curtask = task_of(curr);
  
  		cpuacct_charge(curtask, delta_exec);
  	}

  }
  
  static inline void

  update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);

  }

  /*
   * Task is being enqueued - update stats:
   */

  static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	/*
  	 * Are we enqueueing a waiting task? (for current tasks
  	 * a dequeue/enqueue event is a NOP)
  	 */

  	if (se != cfs_rq->curr)

  		update_stats_wait_start(cfs_rq, se);

  }

  static void

  update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	schedstat_set(se->wait_max, max(se->wait_max,
  			rq_of(cfs_rq)->clock - se->wait_start));

  	schedstat_set(se->wait_start, 0);

  }
  
  static inline void

  update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	/*
  	 * Mark the end of the wait period if dequeueing a
  	 * waiting task:
  	 */

  	if (se != cfs_rq->curr)

  		update_stats_wait_end(cfs_rq, se);

  }
  
  /*
   * 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)

  {
  	/*
  	 * We are starting a new run period:
  	 */

  	se->exec_start = rq_of(cfs_rq)->clock;

  }

  /**************************************************
   * Scheduling class queueing methods:
   */

  static void
  account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
  {
  	update_load_add(&cfs_rq->load, se->load.weight);
  	cfs_rq->nr_running++;
  	se->on_rq = 1;
  }
  
  static void
  account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
  {
  	update_load_sub(&cfs_rq->load, se->load.weight);
  	cfs_rq->nr_running--;
  	se->on_rq = 0;
  }

  static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  #ifdef CONFIG_SCHEDSTATS
  	if (se->sleep_start) {

  		u64 delta = rq_of(cfs_rq)->clock - 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 = rq_of(cfs_rq)->clock - 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;

  
  		/*
  		 * Blocking time is in units of nanosecs, so shift by 20 to
  		 * get a milliseconds-range estimation of the amount of
  		 * time that the task spent sleeping:
  		 */
  		if (unlikely(prof_on == SLEEP_PROFILING)) {

  			struct task_struct *tsk = task_of(se);

  			profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
  				     delta >> 20);
  		}

  	}
  #endif
  }

  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)
  {

  	u64 vruntime;

  	vruntime = cfs_rq->min_vruntime;

  	if (sched_feat(TREE_AVG)) {

  		struct sched_entity *last = __pick_last_entity(cfs_rq);
  		if (last) {

  			vruntime += last->vruntime;
  			vruntime >>= 1;

  		}

  	} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)

  		vruntime += sched_vslice(cfs_rq)/2;

  	/*
  	 * 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_add(cfs_rq, se);

  	if (!initial) {

  		/* sleeps upto a single latency don't count. */

  		if (sched_feat(NEW_FAIR_SLEEPERS) && entity_is_task(se))

  			vruntime -= sysctl_sched_latency;

  		/* ensure we never gain time by being placed backwards. */
  		vruntime = max_vruntime(se->vruntime, vruntime);

  	}

  	se->vruntime = vruntime;

  }
  
  static void

  enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)

  {
  	/*

  	 * Update run-time statistics of the 'current'.

  	 */

  	update_curr(cfs_rq);

  	if (wakeup) {

  		place_entity(cfs_rq, se, 0);

  		enqueue_sleeper(cfs_rq, se);

  	}

  	update_stats_enqueue(cfs_rq, se);

  	check_spread(cfs_rq, se);

  	if (se != cfs_rq->curr)
  		__enqueue_entity(cfs_rq, se);

  	account_entity_enqueue(cfs_rq, se);

  }
  
  static void

  dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)

  {

  	/*
  	 * Update run-time statistics of the 'current'.
  	 */
  	update_curr(cfs_rq);

  	update_stats_dequeue(cfs_rq, se);

  	if (sleep) {

  #ifdef CONFIG_SCHEDSTATS

  		if (entity_is_task(se)) {
  			struct task_struct *tsk = task_of(se);
  
  			if (tsk->state & TASK_INTERRUPTIBLE)

  				se->sleep_start = rq_of(cfs_rq)->clock;

  			if (tsk->state & TASK_UNINTERRUPTIBLE)

  				se->block_start = rq_of(cfs_rq)->clock;

  		}

  #endif

  	}

  	if (se != cfs_rq->curr)

  		__dequeue_entity(cfs_rq, se);
  	account_entity_dequeue(cfs_rq, 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 ideal_runtime, delta_exec;

  	ideal_runtime = sched_slice(cfs_rq, curr);

  	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;

  	if (delta_exec > ideal_runtime)

  		resched_task(rq_of(cfs_rq)->curr);
  }

  static void

  set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)

  {

  	/* 'current' is not kept within the tree. */
  	if (se->on_rq) {
  		/*
  		 * 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.
  		 */
  		update_stats_wait_end(cfs_rq, se);
  		__dequeue_entity(cfs_rq, se);
  	}

  	update_stats_curr_start(cfs_rq, se);

  	cfs_rq->curr = se;

  #ifdef CONFIG_SCHEDSTATS
  	/*
  	 * Track our maximum slice length, if the CPU's load is at
  	 * least twice that of our own weight (i.e. dont track it
  	 * when there are only lesser-weight tasks around):
  	 */

  	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {

  		se->slice_max = max(se->slice_max,
  			se->sum_exec_runtime - se->prev_sum_exec_runtime);
  	}
  #endif

  	se->prev_sum_exec_runtime = se->sum_exec_runtime;

  }

  static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)

  {

  	struct sched_entity *se = NULL;

  	if (first_fair(cfs_rq)) {
  		se = __pick_next_entity(cfs_rq);
  		set_next_entity(cfs_rq, se);
  	}

  
  	return se;
  }

  static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)

  {
  	/*
  	 * 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);

  	check_spread(cfs_rq, prev);

  	if (prev->on_rq) {

  		update_stats_wait_start(cfs_rq, prev);

  		/* Put 'current' back into the tree. */
  		__enqueue_entity(cfs_rq, prev);
  	}

  	cfs_rq->curr = NULL;

  }
  
  static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
  {

  	/*

  	 * Update run-time statistics of the 'current'.

  	 */

  	update_curr(cfs_rq);

  	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))

  		check_preempt_tick(cfs_rq, curr);

  }
  
  /**************************************************
   * 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)
  {

  	return cfs_rq->tg->cfs_rq[this_cpu];

  }
  
  /* 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) entities belong to the same group ? */
  static inline int
  is_same_group(struct sched_entity *se, struct sched_entity *pse)

  {

  	if (se->cfs_rq == pse->cfs_rq)

  		return 1;
  
  	return 0;
  }

  static inline struct sched_entity *parent_entity(struct sched_entity *se)
  {
  	return se->parent;
  }

  #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 sched_entity *se, struct sched_entity *pse)

  {
  	return 1;
  }

  static inline struct sched_entity *parent_entity(struct sched_entity *se)
  {
  	return NULL;
  }

  #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)

  {
  	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);

  		wakeup = 1;

  	}
  }
  
  /*
   * 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)

  {
  	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);

  		/* Don't dequeue parent if it has other entities besides us */
  		if (cfs_rq->load.weight)
  			break;

  		sleep = 1;

  	}
  }
  
  /*

   * sched_yield() support is very simple - we dequeue and enqueue.
   *
   * If compat_yield is turned on then we requeue to the end of the tree.

   */

  static void yield_task_fair(struct rq *rq)

  {

  	struct task_struct *curr = rq->curr;
  	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
  	struct sched_entity *rightmost, *se = &curr->se;

  
  	/*

  	 * Are we the only task in the tree?
  	 */
  	if (unlikely(cfs_rq->nr_running == 1))
  		return;

  	if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {

  		__update_rq_clock(rq);
  		/*

  		 * Update run-time statistics of the 'current'.

  		 */

  		update_curr(cfs_rq);

  
  		return;
  	}
  	/*
  	 * Find the rightmost entry in the rbtree:

  	 */

  	rightmost = __pick_last_entity(cfs_rq);

  	/*
  	 * Already in the rightmost position?
  	 */

  	if (unlikely(rightmost->vruntime < se->vruntime))

  		return;
  
  	/*
  	 * Minimally necessary key value to be last in the tree:

  	 * Upon rescheduling, sched_class::put_prev_task() will place
  	 * 'current' within the tree based on its new key value.

  	 */

  	se->vruntime = rightmost->vruntime + 1;

  }
  
  /*
   * Preempt the current task with a newly woken task if needed:
   */

  static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)

  {
  	struct task_struct *curr = rq->curr;

  	struct cfs_rq *cfs_rq = task_cfs_rq(curr);

  	struct sched_entity *se = &curr->se, *pse = &p->se;

  	unsigned long gran;

  
  	if (unlikely(rt_prio(p->prio))) {

  		update_rq_clock(rq);

  		update_curr(cfs_rq);

  		resched_task(curr);
  		return;
  	}

  	/*
  	 * Batch tasks do not preempt (their preemption is driven by
  	 * the tick):
  	 */
  	if (unlikely(p->policy == SCHED_BATCH))
  		return;

  	if (!sched_feat(WAKEUP_PREEMPT))
  		return;

  	while (!is_same_group(se, pse)) {
  		se = parent_entity(se);
  		pse = parent_entity(pse);

  	}

  	gran = sysctl_sched_wakeup_granularity;
  	if (unlikely(se->load.weight != NICE_0_LOAD))
  		gran = calc_delta_fair(gran, &se->load);

  	if (pse->vruntime + gran < se->vruntime)

  		resched_task(curr);

  }

  static struct task_struct *pick_next_task_fair(struct rq *rq)

  {
  	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);

  		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)

  {
  	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);

  	}
  }

  #ifdef CONFIG_SMP

  /**************************************************
   * 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 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);
  }

  #ifdef CONFIG_FAIR_GROUP_SCHED

  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 = cfs_rq->curr;
  	if (!curr)
  		curr = __pick_next_entity(cfs_rq);

  	p = task_of(curr);
  
  	return p->prio;
  }

  #endif

  static unsigned long

  load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,

  		  unsigned long max_load_move,

  		  struct sched_domain *sd, enum cpu_idle_type idle,
  		  int *all_pinned, int *this_best_prio)

  {
  	struct cfs_rq *busy_cfs_rq;

  	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) {

  #ifdef CONFIG_FAIR_GROUP_SCHED

  		struct cfs_rq *this_cfs_rq;

  		long imbalance;

  		unsigned long maxload;

  
  		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);
  #else

  # define maxload rem_load_move

  #endif

  		/*
  		 * pass busy_cfs_rq argument into

  		 * load_balance_[start|next]_fair iterators
  		 */
  		cfs_rq_iterator.arg = busy_cfs_rq;

  		rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
  					       maxload, sd, idle, all_pinned,
  					       this_best_prio,
  					       &cfs_rq_iterator);

  		if (rem_load_move <= 0)

  			break;
  	}

  	return max_load_move - rem_load_move;

  }

  static int
  move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
  		   struct sched_domain *sd, enum cpu_idle_type idle)
  {
  	struct cfs_rq *busy_cfs_rq;
  	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) {
  		/*
  		 * pass busy_cfs_rq argument into
  		 * load_balance_[start|next]_fair iterators
  		 */
  		cfs_rq_iterator.arg = busy_cfs_rq;
  		if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
  				       &cfs_rq_iterator))
  		    return 1;
  	}
  
  	return 0;
  }

  #endif

  /*
   * 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);
  	}
  }

  #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)

  /*
   * 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, *curr = cfs_rq->curr;

  	int this_cpu = smp_processor_id();

  
  	sched_info_queued(p);

  	update_curr(cfs_rq);

  	place_entity(cfs_rq, se, 1);

  	/* 'curr' will be NULL if the child belongs to a different group */

  	if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&

  			curr && curr->vruntime < se->vruntime) {

  		/*

  		 * Upon rescheduling, sched_class::put_prev_task() will place
  		 * 'current' within the tree based on its new key value.
  		 */

  		swap(curr->vruntime, se->vruntime);

  	}

  	enqueue_task_fair(rq, p, 0);

  	resched_task(rq->curr);

  }

  /* 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 sched_entity *se = &rq->curr->se;
  
  	for_each_sched_entity(se)
  		set_next_entity(cfs_rq_of(se), se);
  }

  /*
   * All the scheduling class methods:
   */

  static const struct sched_class fair_sched_class = {
  	.next			= &idle_sched_class,

  	.enqueue_task		= enqueue_task_fair,
  	.dequeue_task		= dequeue_task_fair,
  	.yield_task		= yield_task_fair,

  	.check_preempt_curr	= check_preempt_wakeup,

  
  	.pick_next_task		= pick_next_task_fair,
  	.put_prev_task		= put_prev_task_fair,

  #ifdef CONFIG_SMP

  	.load_balance		= load_balance_fair,

  	.move_one_task		= move_one_task_fair,

  #endif

  	.set_curr_task          = set_curr_task_fair,

  	.task_tick		= task_tick_fair,
  	.task_new		= task_new_fair,
  };
  
  #ifdef CONFIG_SCHED_DEBUG

  static void print_cfs_stats(struct seq_file *m, int cpu)

  {

  	struct cfs_rq *cfs_rq;

  #ifdef CONFIG_FAIR_GROUP_SCHED
  	print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs);
  #endif

  	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)

  		print_cfs_rq(m, cpu, cfs_rq);

  }
  #endif