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: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 62830ea..1b7399d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -273,6 +273,7 @@
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 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 @@
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 @@
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 @@
#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++)