Bharata B Rao
2008-09-25T04:24:19Z

Oops, missed the subject line in the last post :(

[repost]

sched: Maintain only task entities in cfs_rq->tasks list.

cfs_rq->tasks list is used by the load balancer to iterate
over all the tasks. Currently it holds all the entities
(both task and group entities) because of which there is
a need to check for group entities explicitly during load
balancing. This patch changes the cfs_rq->tasks list to
hold only task entities.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Ingo Molnar <mingo@elte.hu>
---
kernel/sched_fair.c | 26 +++++++++-----------------
1 file changed, 9 insertions(+), 17 deletions(-)

--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -586,11 +586,12 @@ account_entity_enqueue(struct cfs_rq *cf
update_load_add(&cfs_rq->load, se->load.weight);
if (!parent_entity(se))
inc_cpu_load(rq_of(cfs_rq), se->load.weight);
- if (entity_is_task(se))
+ if (entity_is_task(se)) {
add_cfs_task_weight(cfs_rq, se->load.weight);
+ list_add(&se->group_node, &cfs_rq->tasks);
+ }
cfs_rq->nr_running++;
se->on_rq = 1;
- list_add(&se->group_node, &cfs_rq->tasks);
}

static void
@@ -599,11 +600,12 @@ account_entity_dequeue(struct cfs_rq *cf
update_load_sub(&cfs_rq->load, se->load.weight);
if (!parent_entity(se))
dec_cpu_load(rq_of(cfs_rq), se->load.weight);
- if (entity_is_task(se))
+ if (entity_is_task(se)) {
add_cfs_task_weight(cfs_rq, -se->load.weight);
+ list_del_init(&se->group_node);
+ }
cfs_rq->nr_running--;
se->on_rq = 0;
- list_del_init(&se->group_node);
}

static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
@@ -1445,19 +1447,9 @@ __load_balance_iterator(struct cfs_rq *c
if (next == &cfs_rq->tasks)
return NULL;

- /* Skip over entities that are not tasks */
- do {
- se = list_entry(next, struct sched_entity, group_node);
- next = next->next;
- } while (next != &cfs_rq->tasks && !entity_is_task(se));
-
- if (next == &cfs_rq->tasks)
- return NULL;
-
- cfs_rq->balance_iterator = next;
-
- if (entity_is_task(se))
- p = task_of(se);
+ se = list_entry(next, struct sched_entity, group_node);
+ p = task_of(se);
+ cfs_rq->balance_iterator = next->next;

return p;
}