sched: group-scheduler core

Add interface to control cpu bandwidth allocation to task-groups.

(not yet configurable, due to missing CONFIG_CONTAINERS)

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>

5 files changed, 350 insertions, 18 deletions

diff --git a/init/Kconfig b/init/Kconfig
index d54d0cadcc06..11c6762a6529 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -281,6 +281,15 @@ config CPUSETS
 
           Say N if unsure.
 
+config FAIR_GROUP_SCHED
+        bool "Fair group scheduler"
+        depends on EXPERIMENTAL && CONTAINERS
+        help
+          This option enables you to group tasks and control CPU resource
+          allocation to such groups.
+
+          Say N if unsure.
+
 config SYSFS_DEPRECATED
         bool "Create deprecated sysfs files"
         default y
diff --git a/kernel/sched.c b/kernel/sched.c
index 4ad789d268fe..b2688ce54b11 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -171,6 +171,58 @@ struct rt_prio_array {
         struct list_head queue[MAX_RT_PRIO];
 };
 
+#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 */
+        struct cfs_rq **cfs_rq;
+        unsigned long shares;
+};
+
+/* Default task group's sched entity on each cpu */
+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];
+
+/* 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,
+                                        };
+
+/* 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);
+}
+
+/* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
+static inline void set_task_cfs_rq(struct task_struct *p)
+{
+        p->se.cfs_rq = task_grp(p)->cfs_rq[task_cpu(p)];
+        p->se.parent = task_grp(p)->se[task_cpu(p)];
+}
+
+#else
+
+static inline void set_task_cfs_rq(struct task_struct *p) { }
+
+#endif  /* CONFIG_FAIR_GROUP_SCHED */
+
 /* CFS-related fields in a runqueue */
 struct cfs_rq {
         struct load_weight load;
@@ -197,6 +249,7 @@ struct cfs_rq {
          * list is used during load balance.
          */
         struct list_head leaf_cfs_rq_list; /* Better name : task_cfs_rq_list? */
+        struct task_grp *tg;    /* group that "owns" this runqueue */
 #endif
 };
 
@@ -419,18 +472,6 @@ unsigned long long cpu_clock(int cpu)
         return now;
 }
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
-/* Change a task's ->cfs_rq if it moves across CPUs */
-static inline void set_task_cfs_rq(struct task_struct *p)
-{
-        p->se.cfs_rq = &task_rq(p)->cfs;
-}
-#else
-static inline void set_task_cfs_rq(struct task_struct *p)
-{
-}
-#endif
-
 #ifndef prepare_arch_switch
 # define prepare_arch_switch(next)      do { } while (0)
 #endif
@@ -970,8 +1011,8 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
 {
 #ifdef CONFIG_SMP
         task_thread_info(p)->cpu = cpu;
-        set_task_cfs_rq(p);
 #endif
+        set_task_cfs_rq(p);
 }
 
 #ifdef CONFIG_SMP
@@ -3885,8 +3926,11 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 
         oldprio = p->prio;
         on_rq = p->se.on_rq;
-        if (on_rq)
+        if (on_rq) {
                 dequeue_task(rq, p, 0);
+                if (task_running(rq, p))
+                        p->sched_class->put_prev_task(rq, p);
+        }
 
         if (rt_prio(prio))
                 p->sched_class = &rt_sched_class;
@@ -3905,6 +3949,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
                 if (task_running(rq, p)) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
+                        p->sched_class->set_curr_task(rq);
                 } else {
                         check_preempt_curr(rq, p);
                 }
@@ -4190,8 +4235,11 @@ recheck:
         }
         update_rq_clock(rq);
         on_rq = p->se.on_rq;
-        if (on_rq)
+        if (on_rq) {
                 deactivate_task(rq, p, 0);
+                if (task_running(rq, p))
+                        p->sched_class->put_prev_task(rq, p);
+        }
         oldprio = p->prio;
         __setscheduler(rq, p, policy, param->sched_priority);
         if (on_rq) {
@@ -4204,6 +4252,7 @@ recheck:
                 if (task_running(rq, p)) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
+                        p->sched_class->set_curr_task(rq);
                 } else {
                         check_preempt_curr(rq, p);
                 }
@@ -6444,7 +6493,25 @@ void __init sched_init(void)
                 init_cfs_rq(&rq->cfs, rq);
 #ifdef CONFIG_FAIR_GROUP_SCHED
                 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
-                list_add(&rq->cfs.leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
+                {
+                        struct cfs_rq *cfs_rq = &per_cpu(init_cfs_rq, i);
+                        struct sched_entity *se =
+                                         &per_cpu(init_sched_entity, i);
+
+                        init_cfs_rq_p[i] = cfs_rq;
+                        init_cfs_rq(cfs_rq, rq);
+                        cfs_rq->tg = &init_task_grp;
+                        list_add(&cfs_rq->leaf_cfs_rq_list,
+                                                         &rq->leaf_cfs_rq_list);
+
+                        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->parent = NULL;
+                }
+                init_task_grp.shares = NICE_0_LOAD;
 #endif
 
                 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@@ -6632,3 +6699,250 @@ void set_curr_task(int cpu, struct task_struct *p)
 }
 
 #endif
+
+#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 *tg;
+        struct cfs_rq *cfs_rq;
+        struct sched_entity *se;
+        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);
+        if (!tg->cfs_rq)
+                goto err;
+        tg->se = kzalloc(sizeof(se) * num_possible_cpus(), GFP_KERNEL);
+        if (!tg->se)
+                goto err;
+
+        for_each_possible_cpu(i) {
+                struct rq *rq = cpu_rq(i);
+
+                cfs_rq = kmalloc_node(sizeof(struct cfs_rq), GFP_KERNEL,
+                                                         cpu_to_node(i));
+                if (!cfs_rq)
+                        goto err;
+
+                se = kmalloc_node(sizeof(struct sched_entity), GFP_KERNEL,
+                                                        cpu_to_node(i));
+                if (!se)
+                        goto err;
+
+                memset(cfs_rq, 0, sizeof(struct cfs_rq));
+                memset(se, 0, sizeof(struct sched_entity));
+
+                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;
+                se->my_q = cfs_rq;
+                se->load.weight = NICE_0_LOAD;
+                se->load.inv_weight = div64_64(1ULL<<32, NICE_0_LOAD);
+                se->parent = NULL;
+        }
+
+        tg->shares = NICE_0_LOAD;
+
+        /* Bind the container to task_grp object we just created */
+        tg->css.container = cont;
+
+        return &tg->css;
+
+err:
+        for_each_possible_cpu(i) {
+                if (tg->cfs_rq && tg->cfs_rq[i])
+                        kfree(tg->cfs_rq[i]);
+                if (tg->se && tg->se[i])
+                        kfree(tg->se[i]);
+        }
+        if (tg->cfs_rq)
+                kfree(tg->cfs_rq);
+        if (tg->se)
+                kfree(tg->se);
+        if (tg)
+                kfree(tg);
+
+        return ERR_PTR(-ENOMEM);
+}
+
+
+/* destroy runqueue etc associated with a task group */
+static void sched_destroy_group(struct container_subsys *ss,
+                                        struct container *cont)
+{
+        struct task_grp *tg = container_tg(cont);
+        struct cfs_rq *cfs_rq;
+        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];
+                kfree(cfs_rq);
+
+                se = tg->se[i];
+                kfree(se);
+        }
+
+        kfree(tg->cfs_rq);
+        kfree(tg->se);
+        kfree(tg);
+}
+
+static int sched_can_attach(struct container_subsys *ss,
+                             struct container *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;
+}
+
+/* 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)
+{
+        int on_rq, running;
+        unsigned long flags;
+        struct rq *rq;
+
+        rq = task_rq_lock(tsk, &flags);
+
+        if (tsk->sched_class != &fair_sched_class)
+                goto done;
+
+        update_rq_clock(rq);
+
+        running = task_running(rq, tsk);
+        on_rq = tsk->se.on_rq;
+
+        if (on_rq) {
+                dequeue_task(rq, tsk, 0);
+                if (unlikely(running))
+                        tsk->sched_class->put_prev_task(rq, tsk);
+        }
+
+        set_task_cfs_rq(tsk);
+
+        if (on_rq) {
+                enqueue_task(rq, tsk, 0);
+                if (unlikely(running))
+                        tsk->sched_class->set_curr_task(rq);
+        }
+
+done:
+        task_rq_unlock(rq, &flags);
+}
+
+static void set_se_shares(struct sched_entity *se, unsigned long shares)
+{
+        struct cfs_rq *cfs_rq = se->cfs_rq;
+        struct rq *rq = cfs_rq->rq;
+        int on_rq;
+
+        spin_lock_irq(&rq->lock);
+
+        on_rq = se->on_rq;
+        if (on_rq)
+                dequeue_entity(cfs_rq, se, 0);
+
+        se->load.weight = shares;
+        se->load.inv_weight = div64_64((1ULL<<32), shares);
+
+        if (on_rq)
+                enqueue_entity(cfs_rq, se, 0);
+
+        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 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;
+
+        buffer[nbytes] = 0;     /* nul-terminate */
+        shareval = simple_strtoul(buffer, NULL, 10);
+
+        tg->shares = shareval;
+        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;
+}
+
+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);
+}
+
+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 */
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ec445cadbb01..12ab9338d563 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -610,8 +610,7 @@ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
  */
 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
 {
-        /* A later patch will take group into account */
-        return &cpu_rq(this_cpu)->cfs;
+        return cfs_rq->tg->cfs_rq[this_cpu];
 }
 
 /* Iterate thr' all leaf cfs_rq's on a runqueue */
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 3503fb2d9f96..5ebf829cdd73 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -50,6 +50,10 @@ static void task_tick_idle(struct rq *rq, struct task_struct *curr)
 {
 }
 
+static void set_curr_task_idle(struct rq *rq)
+{
+}
+
 /*
  * Simple, special scheduling class for the per-CPU idle tasks:
  */
@@ -66,6 +70,7 @@ static struct sched_class idle_sched_class __read_mostly = {
 
         .load_balance           = load_balance_idle,
 
+        .set_curr_task          = set_curr_task_idle,
         .task_tick              = task_tick_idle,
         /* no .task_new for idle tasks */
 };
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 4b87476a02d0..45b339f56aea 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -218,6 +218,10 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
         }
 }
 
+static void set_curr_task_rt(struct rq *rq)
+{
+}
+
 static struct sched_class rt_sched_class __read_mostly = {
         .enqueue_task           = enqueue_task_rt,
         .dequeue_task           = dequeue_task_rt,
@@ -230,5 +234,6 @@ static struct sched_class rt_sched_class __read_mostly = {
 
         .load_balance           = load_balance_rt,
 
+        .set_curr_task          = set_curr_task_rt,
         .task_tick              = task_tick_rt,
 };