Messages in this thread Patch in this message | | | Date | Wed, 03 Nov 2004 01:00:50 +1100 | From | Con Kolivas <> | Subject | [PATCH] add requeue task redo |
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add requeue task redo
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.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Index: linux-2.6.10-rc1-mm2/kernel/sched.c =================================================================== --- linux-2.6.10-rc1-mm2.orig/kernel/sched.c 2004-11-03 00:54:33.157137840 +1100 +++ linux-2.6.10-rc1-mm2/kernel/sched.c 2004-11-03 00:55:48.638171430 +1100 @@ -579,6 +579,16 @@ 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_del(&p->run_list); + list_add_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: @@ -2425,8 +2435,7 @@ void scheduler_tick(void) 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; } @@ -3569,8 +3578,14 @@ 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 [unhandled content-type:application/pgp-signature] | |