From: Con Kolivas We can requeue tasks for cheaper then doing a complete dequeue followed by an enqueue. Add the requeue_task function and perform it where possible. This will be hit frequently by upcoming changes to the requeueing in timeslice granularity. Signed-off-by: Con Kolivas Acked-by: Ingo Molnar Signed-off-by: Andrew Morton --- 25-akpm/kernel/sched.c | 22 ++++++++++++++++++---- 1 files changed, 18 insertions(+), 4 deletions(-) diff -puN kernel/sched.c~sched-add_requeue_task kernel/sched.c --- 25/kernel/sched.c~sched-add_requeue_task 2004-12-03 20:56:31.447979368 -0800 +++ 25-akpm/kernel/sched.c 2004-12-03 20:56:31.454978304 -0800 @@ -601,6 +601,15 @@ static void enqueue_task(struct task_str } /* + * Put task to the end of the run list without the overhead of dequeue + * followed by enqueue. + */ +static void requeue_task(struct task_struct *p, prio_array_t *array) +{ + list_move_tail(&p->run_list, array->queue + p->prio); +} + +/* * Used by the migration code - we pull tasks from the head of the * remote queue so we want these tasks to show up at the head of the * local queue: @@ -2349,8 +2358,7 @@ void scheduler_tick(int user_ticks, int set_tsk_need_resched(p); /* put it at the end of the queue: */ - dequeue_task(p, rq->active); - enqueue_task(p, rq->active); + requeue_task(p, rq->active); } goto out_unlock; } @@ -3449,8 +3457,14 @@ asmlinkage long sys_sched_yield(void) } else if (!rq->expired->nr_active) schedstat_inc(rq, yld_exp_empty); - dequeue_task(current, array); - enqueue_task(current, target); + if (array != target) { + dequeue_task(current, array); + enqueue_task(current, target); + } else + /* + * requeue_task is cheaper so perform that if possible. + */ + requeue_task(current, array); /* * Since we are going to call schedule() anyway, there's _