Commit 354d60c2 authored by Dhaval Giani's avatar Dhaval Giani Committed by Ingo Molnar

sched: mix tasks and groups

This patch allows tasks and groups to exist in the same cfs_rq. With this
change the CFS group scheduling follows a 1/(M+N) model from a 1/(1+N)
fairness model where M tasks and N groups exist at the cfs_rq level.

[a.p.zijlstra@chello.nl: rt bits and assorted fixes]
Signed-off-by: default avatarDhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: default avatarSrivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ea736ed5
......@@ -273,6 +273,7 @@ struct task_group {
struct list_head list;
};
#ifdef CONFIG_USER_SCHED
#ifdef CONFIG_FAIR_GROUP_SCHED
/* Default task group's sched entity on each cpu */
static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
......@@ -284,6 +285,7 @@ static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;
static DEFINE_PER_CPU(struct sched_rt_entity, init_sched_rt_entity);
static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
#endif
#endif
/* task_group_lock serializes add/remove of task groups and also changes to
* a task group's cpu shares.
......@@ -7447,6 +7449,10 @@ static void init_tg_cfs_entry(struct rq *rq, struct task_group *tg,
list_add(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
tg->se[cpu] = se;
/* se could be NULL for init_task_group */
if (!se)
return;
se->cfs_rq = &rq->cfs;
se->my_q = cfs_rq;
se->load.weight = tg->shares;
......@@ -7469,6 +7475,9 @@ static void init_tg_rt_entry(struct rq *rq, struct task_group *tg,
list_add(&rt_rq->leaf_rt_rq_list, &rq->leaf_rt_rq_list);
tg->rt_se[cpu] = rt_se;
if (!rt_se)
return;
rt_se->rt_rq = &rq->rt;
rt_se->my_q = rt_rq;
rt_se->parent = NULL;
......@@ -7539,18 +7548,56 @@ void __init sched_init(void)
#ifdef CONFIG_FAIR_GROUP_SCHED
init_task_group.shares = init_task_group_load;
INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
#ifdef CONFIG_CGROUP_SCHED
/*
* How much cpu bandwidth does init_task_group get?
*
* In case of task-groups formed thr' the cgroup filesystem, it
* gets 100% of the cpu resources in the system. This overall
* system cpu resource is divided among the tasks of
* init_task_group and its child task-groups in a fair manner,
* based on each entity's (task or task-group's) weight
* (se->load.weight).
*
* In other words, if init_task_group has 10 tasks of weight
* 1024) and two child groups A0 and A1 (of weight 1024 each),
* then A0's share of the cpu resource is:
*
* A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
*
* We achieve this by letting init_task_group's tasks sit
* directly in rq->cfs (i.e init_task_group->se[] = NULL).
*/
init_tg_cfs_entry(rq, &init_task_group, &rq->cfs, NULL, i, 1);
#elif defined CONFIG_USER_SCHED
/*
* In case of task-groups formed thr' the user id of tasks,
* init_task_group represents tasks belonging to root user.
* Hence it forms a sibling of all subsequent groups formed.
* In this case, init_task_group gets only a fraction of overall
* system cpu resource, based on the weight assigned to root
* user's cpu share (INIT_TASK_GROUP_LOAD). This is accomplished
* by letting tasks of init_task_group sit in a separate cfs_rq
* (init_cfs_rq) and having one entity represent this group of
* tasks in rq->cfs (i.e init_task_group->se[] != NULL).
*/
init_tg_cfs_entry(rq, &init_task_group,
&per_cpu(init_cfs_rq, i),
&per_cpu(init_sched_entity, i), i, 1);
#endif
#endif /* CONFIG_FAIR_GROUP_SCHED */
rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
#ifdef CONFIG_RT_GROUP_SCHED
INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
#ifdef CONFIG_CGROUP_SCHED
init_tg_rt_entry(rq, &init_task_group, &rq->rt, NULL, i, 1);
#elif defined CONFIG_USER_SCHED
init_tg_rt_entry(rq, &init_task_group,
&per_cpu(init_rt_rq, i),
&per_cpu(init_sched_rt_entity, i), i, 1);
#else
rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
#endif
#endif
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
......
......@@ -1133,6 +1133,17 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
return 0;
}
/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
int depth = 0;
for_each_sched_entity(se)
depth++;
return depth;
}
/*
* Preempt the current task with a newly woken task if needed:
*/
......@@ -1141,6 +1152,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se, *pse = &p->se;
int se_depth, pse_depth;
if (unlikely(rt_prio(p->prio))) {
update_rq_clock(rq);
......@@ -1165,6 +1177,27 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
if (!sched_feat(WAKEUP_PREEMPT))
return;
/*
* preemption test can be made between sibling entities who are in the
* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
* both tasks until we find their ancestors who are siblings of common
* parent.
*/
/* First walk up until both entities are at same depth */
se_depth = depth_se(se);
pse_depth = depth_se(pse);
while (se_depth > pse_depth) {
se_depth--;
se = parent_entity(se);
}
while (pse_depth > se_depth) {
pse_depth--;
pse = parent_entity(pse);
}
while (!is_same_group(se, pse)) {
se = parent_entity(se);
pse = parent_entity(pse);
......@@ -1223,13 +1256,22 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
static struct task_struct *
__load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
{
struct task_struct *p;
struct task_struct *p = NULL;
struct sched_entity *se;
if (!curr)
return NULL;
p = rb_entry(curr, struct task_struct, se.run_node);
cfs_rq->rb_load_balance_curr = rb_next(curr);
/* Skip over entities that are not tasks */
do {
se = rb_entry(curr, struct sched_entity, run_node);
curr = rb_next(curr);
} while (curr && !entity_is_task(se));
cfs_rq->rb_load_balance_curr = curr;
if (entity_is_task(se))
p = task_of(se);
return p;
}
......@@ -1489,9 +1531,6 @@ static void print_cfs_stats(struct seq_file *m, int cpu)
{
struct cfs_rq *cfs_rq;
#ifdef CONFIG_FAIR_GROUP_SCHED
print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs);
#endif
rcu_read_lock();
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
print_cfs_rq(m, cpu, cfs_rq);
......
......@@ -374,11 +374,15 @@ static void update_curr_rt(struct rq *rq)
curr->se.exec_start = rq->clock;
cpuacct_charge(curr, delta_exec);
spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
if (sched_rt_runtime_exceeded(rt_rq))
resched_task(curr);
spin_unlock(&rt_rq->rt_runtime_lock);
for_each_sched_rt_entity(rt_se) {
rt_rq = rt_rq_of_se(rt_se);
spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
if (sched_rt_runtime_exceeded(rt_rq))
resched_task(curr);
spin_unlock(&rt_rq->rt_runtime_lock);
}
}
static inline
......@@ -477,7 +481,6 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
* entries, we must remove entries top - down.
*
* XXX: O(1/2 h^2) because we can only walk up, not down the chain.
* doesn't matter much for now, as h=2 for GROUP_SCHED.
*/
static void dequeue_rt_stack(struct task_struct *p)
{
......
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