[PATCH 5/5] Add fair "control groups" scheduler

[Srivatsa Vaddagiri <vatsa-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

Enable "cgroup" (formerly containers) based fair group scheduling.
This will let administrator create arbitrary groups of tasks (using
"cgroup" psuedo filesystem) and control their cpu bandwidth usage.

Signed-off-by : Srivatsa Vaddagiri <vatsa-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Signed-off-by : Dhaval Giani <dhaval-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>


---
 include/linux/cgroup_subsys.h |    6 ++
 init/Kconfig                  |   24 +++++---
 kernel/sched.c                |  122 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 145 insertions(+), 7 deletions(-)

Index: current/include/linux/cgroup_subsys.h
===================================================================
--- current.orig/include/linux/cgroup_subsys.h
+++ current/include/linux/cgroup_subsys.h
@@ -36,3 +36,9 @@ SUBSYS(mem_cgroup)
 #endif
 
 /* */
+
+#ifdef CONFIG_FAIR_CGROUP_SCHED
+SUBSYS(cpu_cgroup)
+#endif
+
+/* */
Index: current/init/Kconfig
===================================================================
--- current.orig/init/Kconfig
+++ current/init/Kconfig
@@ -327,13 +327,6 @@ config FAIR_GROUP_SCHED
 	  This feature lets cpu scheduler recognize task groups and control cpu
 	  bandwidth allocation to such task groups.
 
-config RESOURCE_COUNTERS
-	bool "Resource counters"
-	help
-	  This option enables controller independent resource accounting
-          infrastructure that works with cgroups
-	depends on CGROUPS
-
 choice
 	depends on FAIR_GROUP_SCHED
 	prompt "Basis for grouping tasks"
@@ -345,8 +338,25 @@ choice
  		  This option will choose userid as the basis for grouping
 		  tasks, thus providing equal cpu bandwidth to each user.
 
+	config FAIR_CGROUP_SCHED
+		bool "Control groups"
+		depends on CGROUPS
+		help
+		   This option allows you to create arbitrary task groups
+		   using the "cgroup" psuedo filesystem and control
+		   the cpu bandwidth allocated to each such task group.
+		   Refer to Documentation/cgroups.txt for more information
+		   on "cgroup" psuedo filesystem.
+
 endchoice
 
+config RESOURCE_COUNTERS
+	bool "Resource counters"
+	help
+	  This option enables controller independent resource accounting
+          infrastructure that works with cgroups
+	depends on CGROUPS
+
 config SYSFS_DEPRECATED
 	bool "Create deprecated sysfs files"
 	default y
Index: current/kernel/sched.c
===================================================================
--- current.orig/kernel/sched.c
+++ current/kernel/sched.c
@@ -179,10 +179,16 @@ EXPORT_SYMBOL_GPL(cpu_clock);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
+#include <linux/cgroup.h>
+
 struct cfs_rq;
 
 /* task group related information */
 struct task_grp {
+#ifdef CONFIG_FAIR_CGROUP_SCHED
+	struct cgroup_subsys_state css;
+#endif
+
 	/* schedulable entities of this group on each cpu */
 	struct sched_entity **se;
 	/* runqueue "owned" by this group on each cpu */
@@ -221,6 +227,9 @@ static inline struct task_grp *task_grp(
 
 #ifdef CONFIG_FAIR_USER_SCHED
 	tg = p->user->tg;
+#elif CONFIG_FAIR_CGROUP_SCHED
+	tg = container_of(task_subsys_state(p, cpu_cgroup_subsys_id),
+				struct task_grp, css);
 #else
 	tg  = &init_task_grp;
 #endif
@@ -6950,3 +6959,116 @@ int sched_group_set_shares(struct task_g
 }
 
 #endif 	/* CONFIG_FAIR_GROUP_SCHED */
+
+#ifdef CONFIG_FAIR_CGROUP_SCHED
+
+/* return corresponding task_grp object of a cgroup */
+static inline struct task_grp *cgroup_tg(struct cgroup *cont)
+{
+	return container_of(cgroup_subsys_state(cont, cpu_cgroup_subsys_id),
+					 struct task_grp, css);
+}
+
+static struct cgroup_subsys_state *
+cpu_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	struct task_grp *tg;
+
+	if (!cont->parent) {
+		/* This is early initialization for the top cgroup */
+		init_task_grp.css.cgroup = cont;
+		return &init_task_grp.css;
+	}
+
+	/* we support only 1-level deep hierarchical scheduler atm */
+	if (cont->parent->parent)
+		return ERR_PTR(-EINVAL);
+
+	tg = sched_create_group();
+	if (IS_ERR(tg))
+		return ERR_PTR(-ENOMEM);
+
+	/* Bind the cgroup to task_grp object we just created */
+	tg->css.cgroup = cont;
+
+	return &tg->css;
+}
+
+static void cpu_cgroup_destroy(struct cgroup_subsys *ss,
+					struct cgroup *cont)
+{
+	struct task_grp *tg = cgroup_tg(cont);
+
+	sched_destroy_group(tg);
+}
+
+static int cpu_cgroup_can_attach(struct cgroup_subsys *ss,
+			     struct cgroup *cont, struct task_struct *tsk)
+{
+	/* We don't support RT-tasks being in separate groups */
+	if (tsk->sched_class != &fair_sched_class)
+		return -EINVAL;
+
+	return 0;
+}
+
+static void
+cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cont,
+			struct cgroup *old_cont, struct task_struct *tsk)
+{
+	sched_move_task(tsk);
+}
+
+static ssize_t cpu_shares_write(struct cgroup *cont, struct cftype *cftype,
+				struct file *file, const char __user *userbuf,
+				size_t nbytes, loff_t *ppos)
+{
+	unsigned long shareval;
+	struct task_grp *tg = cgroup_tg(cont);
+	char buffer[2*sizeof(unsigned long) + 1];
+	int rc;
+
+	if (nbytes > 2*sizeof(unsigned long))	/* safety check */
+		return -E2BIG;
+
+	if (copy_from_user(buffer, userbuf, nbytes))
+		return -EFAULT;
+
+	buffer[nbytes] = 0;	/* nul-terminate */
+	shareval = simple_strtoul(buffer, NULL, 10);
+
+	rc = sched_group_set_shares(tg, shareval);
+
+	return (rc < 0 ? rc : nbytes);
+}
+
+static u64 cpu_shares_read_uint(struct cgroup *cont, struct cftype *cft)
+{
+	struct task_grp *tg = cgroup_tg(cont);
+
+	return (u64) tg->shares;
+}
+
+static struct cftype cpu_shares = {
+	.name = "shares",
+	.read_uint = cpu_shares_read_uint,
+	.write = cpu_shares_write,
+};
+
+static int cpu_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	return cgroup_add_file(cont, ss, &cpu_shares);
+}
+
+struct cgroup_subsys cpu_cgroup_subsys = {
+	.name = "cpu",
+	.create = cpu_cgroup_create,
+	.destroy  = cpu_cgroup_destroy,
+	.can_attach = cpu_cgroup_can_attach,
+	.attach = cpu_cgroup_attach,
+	.populate = cpu_cgroup_populate,
+	.subsys_id = cpu_cgroup_subsys_id,
+	.early_init = 1,
+};
+
+#endif	/* CONFIG_FAIR_CGROUP_SCHED */

-- 
Regards,
vatsa