#include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/seq_file.h>
  #include <linux/proc_fs.h>
  
  #include "sched.h"
  
  /*
   * 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 15
  
  static int show_schedstat(struct seq_file *seq, void *v)
  {
  	int cpu;
  	int mask_len = DIV_ROUND_UP(NR_CPUS, 32) * 9;
  	char *mask_str = kmalloc(mask_len, GFP_KERNEL);
  
  	if (mask_str == NULL)
  		return -ENOMEM;

  	if (v == (void *)1) {
  		seq_printf(seq, "version %d
  ", SCHEDSTAT_VERSION);
  		seq_printf(seq, "timestamp %lu
  ", jiffies);
  	} else {
  		struct rq *rq;

  #ifdef CONFIG_SMP
  		struct sched_domain *sd;
  		int dcount = 0;
  #endif

  		cpu = (unsigned long)(v - 2);
  		rq = cpu_rq(cpu);

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

  		    "cpu%d %u 0 %u %u %u %u %llu %llu %lu",

  		    cpu, rq->yld_count,

  		    rq->sched_count, rq->sched_goidle,

  		    rq->ttwu_count, rq->ttwu_local,
  		    rq->rq_cpu_time,
  		    rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount);
  
  		seq_printf(seq, "
  ");
  
  #ifdef CONFIG_SMP
  		/* domain-specific stats */
  		rcu_read_lock();
  		for_each_domain(cpu, sd) {
  			enum cpu_idle_type itype;
  
  			cpumask_scnprintf(mask_str, mask_len,
  					  sched_domain_span(sd));
  			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);
  		}
  		rcu_read_unlock();
  #endif
  	}
  	kfree(mask_str);
  	return 0;
  }

  /*
   * This itererator needs some explanation.
   * It returns 1 for the header position.
   * This means 2 is cpu 0.
   * In a hotplugged system some cpus, including cpu 0, may be missing so we have
   * to use cpumask_* to iterate over the cpus.
   */
  static void *schedstat_start(struct seq_file *file, loff_t *offset)

  {

  	unsigned long n = *offset;

  	if (n == 0)
  		return (void *) 1;
  
  	n--;
  
  	if (n > 0)
  		n = cpumask_next(n - 1, cpu_online_mask);
  	else
  		n = cpumask_first(cpu_online_mask);
  
  	*offset = n + 1;
  
  	if (n < nr_cpu_ids)
  		return (void *)(unsigned long)(n + 2);
  	return NULL;
  }
  
  static void *schedstat_next(struct seq_file *file, void *data, loff_t *offset)
  {
  	(*offset)++;
  	return schedstat_start(file, offset);
  }
  
  static void schedstat_stop(struct seq_file *file, void *data)
  {
  }
  
  static const struct seq_operations schedstat_sops = {
  	.start = schedstat_start,
  	.next  = schedstat_next,
  	.stop  = schedstat_stop,
  	.show  = show_schedstat,
  };
  
  static int schedstat_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &schedstat_sops);

  }
  
  static const struct file_operations proc_schedstat_operations = {
  	.open    = schedstat_open,
  	.read    = seq_read,
  	.llseek  = seq_lseek,

  	.release = seq_release,

  };
  
  static int __init proc_schedstat_init(void)
  {
  	proc_create("schedstat", 0, NULL, &proc_schedstat_operations);
  	return 0;
  }

  subsys_initcall(proc_schedstat_init);