kernel/cpu_acct.c

   1 /*
   2  * kernel/cpu_acct.c - CPU accounting cgroup subsystem
   3  *
   4  * Copyright (C) Google Inc, 2006
   5  *
   6  * Developed by Paul Menage (menage@google.com) and Balbir Singh
   7  * (balbir@in.ibm.com)
   8  *
   9  */
  10
  11 /*
  12  * Example cgroup subsystem for reporting total CPU usage of tasks in a
  13  * cgroup, along with percentage load over a time interval
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/cgroup.h>
  18 #include <linux/fs.h>
  19 #include <linux/rcupdate.h>
  20
  21 #include <asm/div64.h>
  22
  23 struct cpuacct {
  24         struct cgroup_subsys_state css;
  25         spinlock_t lock;
  26         /* total time used by this class */
  27         cputime64_t time;
  28
  29         /* time when next load calculation occurs */
  30         u64 next_interval_check;
  31
  32         /* time used in current period */
  33         cputime64_t current_interval_time;
  34
  35         /* time used in last period */
  36         cputime64_t last_interval_time;
  37 };
  38
  39 struct cgroup_subsys cpuacct_subsys;
  40
  41 static inline struct cpuacct *cgroup_ca(struct cgroup *cont)
  42 {
  43         return container_of(cgroup_subsys_state(cont, cpuacct_subsys_id),
  44                             struct cpuacct, css);
  45 }
  46
  47 static inline struct cpuacct *task_ca(struct task_struct *task)
  48 {
  49         return container_of(task_subsys_state(task, cpuacct_subsys_id),
  50                             struct cpuacct, css);
  51 }
  52
  53 #define INTERVAL (HZ * 10)
  54
  55 static inline u64 next_interval_boundary(u64 now)
  56 {
  57         /* calculate the next interval boundary beyond the
  58          * current time */
  59         do_div(now, INTERVAL);
  60         return (now + 1) * INTERVAL;
  61 }
  62
  63 static struct cgroup_subsys_state *cpuacct_create(
  64         struct cgroup_subsys *ss, struct cgroup *cont)
  65 {
  66         struct cpuacct *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
  67
  68         if (!ca)
  69                 return ERR_PTR(-ENOMEM);
  70         spin_lock_init(&ca->lock);
  71         ca->next_interval_check = next_interval_boundary(get_jiffies_64());
  72         return &ca->css;
  73 }
  74
  75 static void cpuacct_destroy(struct cgroup_subsys *ss,
  76                             struct cgroup *cont)
  77 {
  78         kfree(cgroup_ca(cont));
  79 }
  80
  81 /* Lazily update the load calculation if necessary. Called with ca locked */
  82 static void cpuusage_update(struct cpuacct *ca)
  83 {
  84         u64 now = get_jiffies_64();
  85
  86         /* If we're not due for an update, return */
  87         if (ca->next_interval_check > now)
  88                 return;
  89
  90         if (ca->next_interval_check <= (now - INTERVAL)) {
  91                 /* If it's been more than an interval since the last
  92                  * check, then catch up - the last interval must have
  93                  * been zero load */
  94                 ca->last_interval_time = 0;
  95                 ca->next_interval_check = next_interval_boundary(now);
  96         } else {
  97                 /* If a steal takes the last interval time negative,
  98                  * then we just ignore it */
  99                 if ((s64)ca->current_interval_time > 0)
 100                         ca->last_interval_time = ca->current_interval_time;
 101                 else
 102                         ca->last_interval_time = 0;
 103                 ca->next_interval_check += INTERVAL;
 104         }
 105         ca->current_interval_time = 0;
 106 }
 107
 108 static u64 cpuusage_read(struct cgroup *cont, struct cftype *cft)
 109 {
 110         struct cpuacct *ca = cgroup_ca(cont);
 111         u64 time;
 112
 113         spin_lock_irq(&ca->lock);
 114         cpuusage_update(ca);
 115         time = cputime64_to_jiffies64(ca->time);
 116         spin_unlock_irq(&ca->lock);
 117
 118         /* Convert 64-bit jiffies to seconds */
 119         time *= 1000;
 120         do_div(time, HZ);
 121         return time;
 122 }
 123
 124 static u64 load_read(struct cgroup *cont, struct cftype *cft)
 125 {
 126         struct cpuacct *ca = cgroup_ca(cont);
 127         u64 time;
 128
 129         /* Find the time used in the previous interval */
 130         spin_lock_irq(&ca->lock);
 131         cpuusage_update(ca);
 132         time = cputime64_to_jiffies64(ca->last_interval_time);
 133         spin_unlock_irq(&ca->lock);
 134
 135         /* Convert time to a percentage, to give the load in the
 136          * previous period */
 137         time *= 100;
 138         do_div(time, INTERVAL);
 139
 140         return time;
 141 }
 142
 143 static struct cftype files[] = {
 144         {
 145                 .name = "usage",
 146                 .read_uint = cpuusage_read,
 147         },
 148         {
 149                 .name = "load",
 150                 .read_uint = load_read,
 151         }
 152 };
 153
 154 static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cont)
 155 {
 156         return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
 157 }
 158
 159 void cpuacct_charge(struct task_struct *task, cputime_t cputime)
 160 {
 161
 162         struct cpuacct *ca;
 163         unsigned long flags;
 164
 165         if (!cpuacct_subsys.active)
 166                 return;
 167         rcu_read_lock();
 168         ca = task_ca(task);
 169         if (ca) {
 170                 spin_lock_irqsave(&ca->lock, flags);
 171                 cpuusage_update(ca);
 172                 ca->time = cputime64_add(ca->time, cputime);
 173                 ca->current_interval_time =
 174                         cputime64_add(ca->current_interval_time, cputime);
 175                 spin_unlock_irqrestore(&ca->lock, flags);
 176         }
 177         rcu_read_unlock();
 178 }
 179
 180 struct cgroup_subsys cpuacct_subsys = {
 181         .name = "cpuacct",
 182         .create = cpuacct_create,
 183         .destroy = cpuacct_destroy,
 184         .populate = cpuacct_populate,
 185         .subsys_id = cpuacct_subsys_id,
 186 };