Task Control Groups: example CPU accounting subsystem
This example demonstrates how to use the generic cgroup subsystem for a
simple resource tracker that counts, for the processes in a cgroup, the
total CPU time used and the %CPU used in the last complete 10 second interval.
Portions contributed by Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Paul Menage <menage@google.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cpu_acct.c b/kernel/cpu_acct.c
new file mode 100644
index 0000000..731e47e
--- /dev/null
+++ b/kernel/cpu_acct.c
@@ -0,0 +1,186 @@
+/*
+ * 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,
+};