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>

1 files changed, 186 insertions, 0 deletions

diff --git a/kernel/cpu_acct.c b/kernel/cpu_acct.c
new file mode 100644
index 000000000000..731e47e7f164
--- /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,
+};