#ifdef CONFIG_SCHEDSTATS
  /*
   * bump this up when changing the output format or the meaning of an existing
   * format, so that tools can adapt (or abort)
   */
  #define SCHEDSTAT_VERSION 14
  
  static int show_schedstat(struct seq_file *seq, void *v)
  {
  	int cpu;
  
  	seq_printf(seq, "version %d
  ", SCHEDSTAT_VERSION);
  	seq_printf(seq, "timestamp %lu
  ", jiffies);
  	for_each_online_cpu(cpu) {
  		struct rq *rq = cpu_rq(cpu);
  #ifdef CONFIG_SMP
  		struct sched_domain *sd;

  		int dcount = 0;

  #endif
  
  		/* runqueue-specific stats */
  		seq_printf(seq,

  		    "cpu%d %u %u %u %u %u %u %u %u %u %llu %llu %lu",

  		    cpu, rq->yld_both_empty,

  		    rq->yld_act_empty, rq->yld_exp_empty, rq->yld_count,
  		    rq->sched_switch, rq->sched_count, rq->sched_goidle,
  		    rq->ttwu_count, rq->ttwu_local,

  		    rq->rq_sched_info.cpu_time,

  		    rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount);

  
  		seq_printf(seq, "
  ");
  
  #ifdef CONFIG_SMP
  		/* domain-specific stats */
  		preempt_disable();
  		for_each_domain(cpu, sd) {
  			enum cpu_idle_type itype;
  			char mask_str[NR_CPUS];
  
  			cpumask_scnprintf(mask_str, NR_CPUS, sd->span);

  			seq_printf(seq, "domain%d %s", dcount++, mask_str);

  			for (itype = CPU_IDLE; itype < CPU_MAX_IDLE_TYPES;
  					itype++) {

  				seq_printf(seq, " %u %u %u %u %u %u %u %u",

  				    sd->lb_count[itype],

  				    sd->lb_balanced[itype],
  				    sd->lb_failed[itype],
  				    sd->lb_imbalance[itype],
  				    sd->lb_gained[itype],
  				    sd->lb_hot_gained[itype],
  				    sd->lb_nobusyq[itype],
  				    sd->lb_nobusyg[itype]);
  			}

  			seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u %u
  ",

  			    sd->alb_count, sd->alb_failed, sd->alb_pushed,
  			    sd->sbe_count, sd->sbe_balanced, sd->sbe_pushed,
  			    sd->sbf_count, sd->sbf_balanced, sd->sbf_pushed,

  			    sd->ttwu_wake_remote, sd->ttwu_move_affine,
  			    sd->ttwu_move_balance);
  		}
  		preempt_enable();
  #endif
  	}
  	return 0;
  }
  
  static int schedstat_open(struct inode *inode, struct file *file)
  {
  	unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
  	char *buf = kmalloc(size, GFP_KERNEL);
  	struct seq_file *m;
  	int res;
  
  	if (!buf)
  		return -ENOMEM;
  	res = single_open(file, show_schedstat, NULL);
  	if (!res) {
  		m = file->private_data;
  		m->buf = buf;
  		m->size = size;
  	} else
  		kfree(buf);
  	return res;
  }
  
  const struct file_operations proc_schedstat_operations = {
  	.open    = schedstat_open,
  	.read    = seq_read,
  	.llseek  = seq_lseek,
  	.release = single_release,
  };
  
  /*
   * Expects runqueue lock to be held for atomicity of update
   */
  static inline void
  rq_sched_info_arrive(struct rq *rq, unsigned long long delta)
  {
  	if (rq) {
  		rq->rq_sched_info.run_delay += delta;

  		rq->rq_sched_info.pcount++;

  	}
  }
  
  /*
   * Expects runqueue lock to be held for atomicity of update
   */
  static inline void
  rq_sched_info_depart(struct rq *rq, unsigned long long delta)
  {
  	if (rq)
  		rq->rq_sched_info.cpu_time += delta;
  }
  # define schedstat_inc(rq, field)	do { (rq)->field++; } while (0)
  # define schedstat_add(rq, field, amt)	do { (rq)->field += (amt); } while (0)

  # define schedstat_set(var, val)	do { var = (val); } while (0)

  #else /* !CONFIG_SCHEDSTATS */
  static inline void
  rq_sched_info_arrive(struct rq *rq, unsigned long long delta)
  {}
  static inline void
  rq_sched_info_depart(struct rq *rq, unsigned long long delta)
  {}
  # define schedstat_inc(rq, field)	do { } while (0)
  # define schedstat_add(rq, field, amt)	do { } while (0)

  # define schedstat_set(var, val)	do { } while (0)

  #endif

  #ifdef CONFIG_SCHEDSTATS

  /*
   * Called when a process is dequeued from the active array and given
   * the cpu.  We should note that with the exception of interactive
   * tasks, the expired queue will become the active queue after the active
   * queue is empty, without explicitly dequeuing and requeuing tasks in the
   * expired queue.  (Interactive tasks may be requeued directly to the
   * active queue, thus delaying tasks in the expired queue from running;
   * see scheduler_tick()).
   *
   * This function is only called from sched_info_arrive(), rather than
   * dequeue_task(). Even though a task may be queued and dequeued multiple
   * times as it is shuffled about, we're really interested in knowing how
   * long it was from the *first* time it was queued to the time that it
   * finally hit a cpu.
   */
  static inline void sched_info_dequeued(struct task_struct *t)
  {
  	t->sched_info.last_queued = 0;
  }
  
  /*
   * Called when a task finally hits the cpu.  We can now calculate how
   * long it was waiting to run.  We also note when it began so that we
   * can keep stats on how long its timeslice is.
   */
  static void sched_info_arrive(struct task_struct *t)
  {
  	unsigned long long now = sched_clock(), delta = 0;
  
  	if (t->sched_info.last_queued)
  		delta = now - t->sched_info.last_queued;
  	sched_info_dequeued(t);
  	t->sched_info.run_delay += delta;
  	t->sched_info.last_arrival = now;

  	t->sched_info.pcount++;

  
  	rq_sched_info_arrive(task_rq(t), delta);
  }
  
  /*
   * Called when a process is queued into either the active or expired
   * array.  The time is noted and later used to determine how long we
   * had to wait for us to reach the cpu.  Since the expired queue will
   * become the active queue after active queue is empty, without dequeuing
   * and requeuing any tasks, we are interested in queuing to either. It
   * is unusual but not impossible for tasks to be dequeued and immediately
   * requeued in the same or another array: this can happen in sched_yield(),
   * set_user_nice(), and even load_balance() as it moves tasks from runqueue
   * to runqueue.
   *
   * This function is only called from enqueue_task(), but also only updates
   * the timestamp if it is already not set.  It's assumed that
   * sched_info_dequeued() will clear that stamp when appropriate.
   */
  static inline void sched_info_queued(struct task_struct *t)
  {
  	if (unlikely(sched_info_on()))
  		if (!t->sched_info.last_queued)
  			t->sched_info.last_queued = sched_clock();
  }
  
  /*
   * Called when a process ceases being the active-running process, either
   * voluntarily or involuntarily.  Now we can calculate how long we ran.
   */
  static inline void sched_info_depart(struct task_struct *t)
  {
  	unsigned long long delta = sched_clock() - t->sched_info.last_arrival;
  
  	t->sched_info.cpu_time += delta;
  	rq_sched_info_depart(task_rq(t), delta);
  }
  
  /*
   * Called when tasks are switched involuntarily due, typically, to expiring
   * their time slice.  (This may also be called when switching to or from
   * the idle task.)  We are only called when prev != next.
   */
  static inline void
  __sched_info_switch(struct task_struct *prev, struct task_struct *next)
  {
  	struct rq *rq = task_rq(prev);
  
  	/*
  	 * prev now departs the cpu.  It's not interesting to record
  	 * stats about how efficient we were at scheduling the idle
  	 * process, however.
  	 */
  	if (prev != rq->idle)
  		sched_info_depart(prev);
  
  	if (next != rq->idle)
  		sched_info_arrive(next);
  }
  static inline void
  sched_info_switch(struct task_struct *prev, struct task_struct *next)
  {
  	if (unlikely(sched_info_on()))
  		__sched_info_switch(prev, next);
  }
  #else
  #define sched_info_queued(t)		do { } while (0)
  #define sched_info_switch(t, next)	do { } while (0)

  #endif /* CONFIG_SCHEDSTATS */