[PATCH] sched: fix SCHED_OTHER balance iterator to include all tasks
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From: Gregory Haskins on 5 May 2008 10:50 Hi Ingo, The follow patch applies to sched-devel. I know the original function was somehow trying to protect against dequeueing by pre-iterating. I am not sure if I captured the intent properly in that regard. What I can say is that the old algorithm would miss tasks, and that is now fixed. It may need further adjustment if I missed the pre-iterating operation. Hi Peter, I was wrong earlier when I mentioned there might be a problem with entity_is_task(). I think this was the root cause of what I was seeing. Sorry for the red-herring. Regards, -Greg ----------------------- sched: fix SCHED_OTHER balance iterator to include all tasks The currently logic inadvertently skips the last task on the run-queue, resulting in missed balance opportunities. Signed-off-by: Gregory Haskins <ghaskins(a)novell.com> Signed-off-by: David Bahi <dbahi(a)novell.com> CC: Ingo Molnar <mingo(a)elte.hu> CC: Peter Zijlstra <peterz(a)infradead.org> --- kernel/sched_fair.c | 19 +++++++------------ 1 files changed, 7 insertions(+), 12 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 87b7300..e8c289a 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1700,23 +1700,18 @@ __load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next) struct task_struct *p = NULL; struct sched_entity *se; - if (next == &cfs_rq->tasks) - return NULL; - - /* Skip over entities that are not tasks */ - do { + while (next != &cfs_rq->tasks) { 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; + /* Skip over entities that are not tasks */ + if (entity_is_task(se)) { + p = task_of(se); + break; + } + } cfs_rq->balance_iterator = next; - - if (entity_is_task(se)) - p = task_of(se); - return p; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |