sched: clean up code under CONFIG_FAIR_GROUP_SCHED

With the view of supporting user-id based fair scheduling (and not just
container-based fair scheduling), this patch renames several functions
and makes them independent of whether they are being used for container
or user-id based fair scheduling.

Also fix a problem reported by KAMEZAWA Hiroyuki (wrt allocating
less-sized array for tg->cfs_rq[] and tf->se[]).
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/sched.h

@@ -136,6 +136,7 @@ extern unsigned long weighted_cpuload(const int cpu);
 
 struct seq_file;
 struct cfs_rq;
+struct task_grp;
 #ifdef CONFIG_SCHED_DEBUG
 extern void proc_sched_show_task(struct task_struct *p, struct seq_file *m);
 extern void proc_sched_set_task(struct task_struct *p);
@@ -1834,6 +1835,17 @@ extern int sched_mc_power_savings, sched_smt_power_savings;
 
 extern void normalize_rt_tasks(void);
 
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+extern struct task_grp init_task_grp;
+
+extern struct task_grp *sched_create_group(void);
+extern void sched_destroy_group(struct task_grp *tg);
+extern void sched_move_task(struct task_struct *tsk);
+extern int sched_group_set_shares(struct task_grp *tg, unsigned long shares);
+
+#endif
+
 #ifdef CONFIG_TASK_XACCT
 static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
 {

init/Kconfig

@@ -282,13 +282,12 @@ config CPUSETS
 	  Say N if unsure.
 
 config FAIR_GROUP_SCHED
-	bool "Fair group scheduler"
-	depends on EXPERIMENTAL && CONTAINERS
+	bool "Fair group cpu scheduler"
+	default n
+	depends on EXPERIMENTAL
 	help
-	  This option enables you to group tasks and control CPU resource
-	  allocation to such groups.
-
-	  Say N if unsure.
+	  This feature lets cpu scheduler recognize task groups and control cpu
+	  bandwidth allocation to such task groups.
 
 config SYSFS_DEPRECATED
 	bool "Create deprecated sysfs files"

kernel/sched.c

@@ -173,13 +173,10 @@ struct rt_prio_array {
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
-#include <linux/container.h>
-
 struct cfs_rq;
 
 /* task group related information */
 struct task_grp {
-	struct container_subsys_state css;
 	/* schedulable entities of this group on each cpu */
 	struct sched_entity **se;
 	/* runqueue "owned" by this group on each cpu */
@@ -192,22 +189,28 @@ static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
 /* Default task group's cfs_rq on each cpu */
 static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;
 
-static struct sched_entity *init_sched_entity_p[CONFIG_NR_CPUS];
-static struct cfs_rq *init_cfs_rq_p[CONFIG_NR_CPUS];
+static struct sched_entity *init_sched_entity_p[NR_CPUS];
+static struct cfs_rq *init_cfs_rq_p[NR_CPUS];
 
 /* Default task group.
  * 	Every task in system belong to this group at bootup.
  */
-static struct task_grp init_task_grp =  {
-					.se     = init_sched_entity_p,
-					.cfs_rq = init_cfs_rq_p,
-					};
+struct task_grp init_task_grp =  {
+				.se     = init_sched_entity_p,
+				.cfs_rq = init_cfs_rq_p,
+				 };
+
+#define INIT_TASK_GRP_LOAD	NICE_0_LOAD
+static int init_task_grp_load = INIT_TASK_GRP_LOAD;
 
 /* return group to which a task belongs */
 static inline struct task_grp *task_grp(struct task_struct *p)
 {
-	return container_of(task_subsys_state(p, cpu_subsys_id),
-				struct task_grp, css);
+	struct task_grp *tg;
+
+	tg  = &init_task_grp;
+
+	return tg;
 }
 
 /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
@@ -250,6 +253,7 @@ struct cfs_rq {
 	 */
 	struct list_head leaf_cfs_rq_list; /* Better name : task_cfs_rq_list? */
 	struct task_grp *tg;    /* group that "owns" this runqueue */
+	struct rcu_head rcu;
 #endif
 };
 
@@ -6513,11 +6517,12 @@ void __init sched_init(void)
  			init_sched_entity_p[i] = se;
  			se->cfs_rq = &rq->cfs;
  			se->my_q = cfs_rq;
- 			se->load.weight = NICE_0_LOAD;
-			se->load.inv_weight = div64_64(1ULL<<32, NICE_0_LOAD);
+ 			se->load.weight = init_task_grp_load;
+			se->load.inv_weight =
+				 div64_64(1ULL<<32, init_task_grp_load);
  			se->parent = NULL;
  		}
-		init_task_grp.shares = NICE_0_LOAD;
+		init_task_grp.shares = init_task_grp_load;
 #endif
 
 		for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@@ -6707,45 +6712,28 @@ void set_curr_task(int cpu, struct task_struct *p)
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
-/* return corresponding task_grp object of a container */
-static inline struct task_grp *container_tg(struct container *cont)
-{
-	return container_of(container_subsys_state(cont, cpu_subsys_id),
-					 struct task_grp, css);
-}
-
 /* allocate runqueue etc for a new task group */
-static struct container_subsys_state *
-sched_create_group(struct container_subsys *ss, struct container *cont)
+struct task_grp *sched_create_group(void)
 {
 	struct task_grp *tg;
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se;
+	struct rq *rq;
 	int i;
 
-	if (!cont->parent) {
-		/* This is early initialization for the top container */
-		init_task_grp.css.container = cont;
-		return &init_task_grp.css;
-	}
-
-	/* we support only 1-level deep hierarchical scheduler atm */
-	if (cont->parent->parent)
-		return ERR_PTR(-EINVAL);
-
 	tg = kzalloc(sizeof(*tg), GFP_KERNEL);
 	if (!tg)
 		return ERR_PTR(-ENOMEM);
 
-	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * num_possible_cpus(), GFP_KERNEL);
+	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * NR_CPUS, GFP_KERNEL);
 	if (!tg->cfs_rq)
 		goto err;
-	tg->se = kzalloc(sizeof(se) * num_possible_cpus(), GFP_KERNEL);
+	tg->se = kzalloc(sizeof(se) * NR_CPUS, GFP_KERNEL);
 	if (!tg->se)
 		goto err;
 
 	for_each_possible_cpu(i) {
-		struct rq *rq = cpu_rq(i);
+		rq = cpu_rq(i);
 
 		cfs_rq = kmalloc_node(sizeof(struct cfs_rq), GFP_KERNEL,
 							 cpu_to_node(i));
@@ -6763,7 +6751,6 @@ sched_create_group(struct container_subsys *ss, struct container *cont)
 		tg->cfs_rq[i] = cfs_rq;
 		init_cfs_rq(cfs_rq, rq);
 		cfs_rq->tg = tg;
-		list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
 
 		tg->se[i] = se;
 		se->cfs_rq = &rq->cfs;
@@ -6773,12 +6760,15 @@ sched_create_group(struct container_subsys *ss, struct container *cont)
 		se->parent = NULL;
 	}
 
-	tg->shares = NICE_0_LOAD;
+	for_each_possible_cpu(i) {
+		rq = cpu_rq(i);
+		cfs_rq = tg->cfs_rq[i];
+		list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
+	}
 
-	/* Bind the container to task_grp object we just created */
-	tg->css.container = cont;
+	tg->shares = NICE_0_LOAD;
 
-	return &tg->css;
+	return tg;
 
 err:
 	for_each_possible_cpu(i) {
@@ -6797,24 +6787,14 @@ sched_create_group(struct container_subsys *ss, struct container *cont)
 	return ERR_PTR(-ENOMEM);
 }
 
-
-/* destroy runqueue etc associated with a task group */
-static void sched_destroy_group(struct container_subsys *ss,
-					struct container *cont)
+/* rcu callback to free various structures associated with a task group */
+static void free_sched_group(struct rcu_head *rhp)
 {
-	struct task_grp *tg = container_tg(cont);
-	struct cfs_rq *cfs_rq;
+	struct cfs_rq *cfs_rq = container_of(rhp, struct cfs_rq, rcu);
+	struct task_grp *tg = cfs_rq->tg;
 	struct sched_entity *se;
 	int i;
 
-	for_each_possible_cpu(i) {
-		cfs_rq = tg->cfs_rq[i];
-		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
-	}
-
-	/* wait for possible concurrent references to cfs_rqs complete */
-	synchronize_sched();
-
 	/* now it should be safe to free those cfs_rqs */
 	for_each_possible_cpu(i) {
 		cfs_rq = tg->cfs_rq[i];
@@ -6829,19 +6809,29 @@ static void sched_destroy_group(struct container_subsys *ss,
 	kfree(tg);
 }
 
-static int sched_can_attach(struct container_subsys *ss,
-			     struct container *cont, struct task_struct *tsk)
+/* Destroy runqueue etc associated with a task group */
+void sched_destroy_group(struct task_grp *tg)
 {
-	/* We don't support RT-tasks being in separate groups */
-	if (tsk->sched_class != &fair_sched_class)
-		return -EINVAL;
+	struct cfs_rq *cfs_rq;
+	int i;
 
-	return 0;
+	for_each_possible_cpu(i) {
+		cfs_rq = tg->cfs_rq[i];
+		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
+	}
+
+	cfs_rq = tg->cfs_rq[0];
+
+	/* wait for possible concurrent references to cfs_rqs complete */
+	call_rcu(&cfs_rq->rcu, free_sched_group);
 }
 
-/* change task's runqueue when it moves between groups */
-static void sched_move_task(struct container_subsys *ss, struct container *cont,
-			struct container *old_cont, struct task_struct *tsk)
+/* change task's runqueue when it moves between groups.
+ * 	The caller of this function should have put the task in its new group
+ * 	by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
+ * 	reflect its new group.
+ */
+void sched_move_task(struct task_struct *tsk)
 {
 	int on_rq, running;
 	unsigned long flags;
@@ -6896,58 +6886,20 @@ static void set_se_shares(struct sched_entity *se, unsigned long shares)
 	spin_unlock_irq(&rq->lock);
 }
 
-static ssize_t cpu_shares_write(struct container *cont, struct cftype *cftype,
-				struct file *file, const char __user *userbuf,
-				size_t nbytes, loff_t *ppos)
+int sched_group_set_shares(struct task_grp *tg, unsigned long shares)
 {
 	int i;
-	unsigned long shareval;
-	struct task_grp *tg = container_tg(cont);
-	char buffer[2*sizeof(unsigned long) + 1];
-
-	if (nbytes > 2*sizeof(unsigned long))	/* safety check */
-		return -E2BIG;
 
-	if (copy_from_user(buffer, userbuf, nbytes))
-		return -EFAULT;
+	if (tg->shares == shares)
+		return 0;
 
-	buffer[nbytes] = 0;	/* nul-terminate */
-	shareval = simple_strtoul(buffer, NULL, 10);
+	/* return -EINVAL if the new value is not sane */
 
-	tg->shares = shareval;
+	tg->shares = shares;
 	for_each_possible_cpu(i)
-		set_se_shares(tg->se[i], shareval);
-
-	return nbytes;
-}
-
-static u64 cpu_shares_read_uint(struct container *cont, struct cftype *cft)
-{
-	struct task_grp *tg = container_tg(cont);
-
-	return (u64) tg->shares;
-}
+		set_se_shares(tg->se[i], shares);
 
-struct cftype cpuctl_share = {
-	.name = "shares",
-	.read_uint = cpu_shares_read_uint,
-	.write = cpu_shares_write,
-};
-
-static int sched_populate(struct container_subsys *ss, struct container *cont)
-{
-	return container_add_file(cont, ss, &cpuctl_share);
+	return 0;
 }
 
-struct container_subsys cpu_subsys = {
-	.name = "cpu",
-	.create = sched_create_group,
-	.destroy  = sched_destroy_group,
-	.can_attach = sched_can_attach,
-	.attach = sched_move_task,
-	.populate = sched_populate,
-	.subsys_id = cpu_subsys_id,
-	.early_init = 1,
-};
-
-#endif	/* CONFIG_FAIR_GROUP_SCHED */
+#endif 	/* CONFIG_FAIR_GROUP_SCHED */

kernel/sched_fair.c

@@ -877,7 +877,10 @@ static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
 	if (!cfs_rq->nr_running)
 		return MAX_PRIO;
 
-	curr = __pick_next_entity(cfs_rq);
+	curr = cfs_rq->curr;
+	if (!curr)
+		curr = __pick_next_entity(cfs_rq);
+
 	p = task_of(curr);
 
 	return p->prio;