cpu_acct.c
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/*
* kernel/cpu_acct.c - CPU accounting cgroup subsystem
*
* Copyright (C) Google Inc, 2006
*
* Developed by Paul Menage (menage@google.com) and Balbir Singh
* (balbir@in.ibm.com)
*
*/
/*
* Example cgroup subsystem for reporting total CPU usage of tasks in a
* cgroup, along with percentage load over a time interval
*/
#include <linux/module.h>
#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/rcupdate.h>
#include <asm/div64.h>
struct cpuacct {
struct cgroup_subsys_state css;
spinlock_t lock;
/* total time used by this class */
cputime64_t time;
/* time when next load calculation occurs */
u64 next_interval_check;
/* time used in current period */
cputime64_t current_interval_time;
/* time used in last period */
cputime64_t last_interval_time;
};
struct cgroup_subsys cpuacct_subsys;
static inline struct cpuacct *cgroup_ca(struct cgroup *cont)
{
return container_of(cgroup_subsys_state(cont, cpuacct_subsys_id),
struct cpuacct, css);
}
static inline struct cpuacct *task_ca(struct task_struct *task)
{
return container_of(task_subsys_state(task, cpuacct_subsys_id),
struct cpuacct, css);
}
#define INTERVAL (HZ * 10)
static inline u64 next_interval_boundary(u64 now)
{
/* calculate the next interval boundary beyond the
* current time */
do_div(now, INTERVAL);
return (now + 1) * INTERVAL;
}
static struct cgroup_subsys_state *cpuacct_create(
struct cgroup_subsys *ss, struct cgroup *cont)
{
struct cpuacct *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
if (!ca)
return ERR_PTR(-ENOMEM);
spin_lock_init(&ca->lock);
ca->next_interval_check = next_interval_boundary(get_jiffies_64());
return &ca->css;
}
static void cpuacct_destroy(struct cgroup_subsys *ss,
struct cgroup *cont)
{
kfree(cgroup_ca(cont));
}
/* Lazily update the load calculation if necessary. Called with ca locked */
static void cpuusage_update(struct cpuacct *ca)
{
u64 now = get_jiffies_64();
/* If we're not due for an update, return */
if (ca->next_interval_check > now)
return;
if (ca->next_interval_check <= (now - INTERVAL)) {
/* If it's been more than an interval since the last
* check, then catch up - the last interval must have
* been zero load */
ca->last_interval_time = 0;
ca->next_interval_check = next_interval_boundary(now);
} else {
/* If a steal takes the last interval time negative,
* then we just ignore it */
if ((s64)ca->current_interval_time > 0)
ca->last_interval_time = ca->current_interval_time;
else
ca->last_interval_time = 0;
ca->next_interval_check += INTERVAL;
}
ca->current_interval_time = 0;
}
static u64 cpuusage_read(struct cgroup *cont, struct cftype *cft)
{
struct cpuacct *ca = cgroup_ca(cont);
u64 time;
spin_lock_irq(&ca->lock);
cpuusage_update(ca);
time = cputime64_to_jiffies64(ca->time);
spin_unlock_irq(&ca->lock);
/* Convert 64-bit jiffies to seconds */
time *= 1000;
do_div(time, HZ);
return time;
}
static u64 load_read(struct cgroup *cont, struct cftype *cft)
{
struct cpuacct *ca = cgroup_ca(cont);
u64 time;
/* Find the time used in the previous interval */
spin_lock_irq(&ca->lock);
cpuusage_update(ca);
time = cputime64_to_jiffies64(ca->last_interval_time);
spin_unlock_irq(&ca->lock);
/* Convert time to a percentage, to give the load in the
* previous period */
time *= 100;
do_div(time, INTERVAL);
return time;
}
static struct cftype files[] = {
{
.name = "usage",
.read_uint = cpuusage_read,
},
{
.name = "load",
.read_uint = load_read,
}
};
static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
}
void cpuacct_charge(struct task_struct *task, cputime_t cputime)
{
struct cpuacct *ca;
unsigned long flags;
if (!cpuacct_subsys.active)
return;
rcu_read_lock();
ca = task_ca(task);
if (ca) {
spin_lock_irqsave(&ca->lock, flags);
cpuusage_update(ca);
ca->time = cputime64_add(ca->time, cputime);
ca->current_interval_time =
cputime64_add(ca->current_interval_time, cputime);
spin_unlock_irqrestore(&ca->lock, flags);
}
rcu_read_unlock();
}
struct cgroup_subsys cpuacct_subsys = {
.name = "cpuacct",
.create = cpuacct_create,
.destroy = cpuacct_destroy,
.populate = cpuacct_populate,
.subsys_id = cpuacct_subsys_id,
};