Re: sched:

Peter Zijlstra
2008-09-25T09:14:46Z

On Thu, 2008-09-25 at 09:51 +0530, Bharata B Rao wrote:
> Hi,
>
> 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.

Looks fine. Thanks Bharata!

> 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;
> }
>
> Regards,
> Bharata.