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/*
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* idle-task scheduling class.
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*
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* (NOTE: these are not related to SCHED_IDLE tasks which are
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* handled in sched_fair.c)
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*/
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#ifdef CONFIG_SMP
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static int select_task_rq_idle(struct task_struct *p, int sync)
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|
{
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return task_cpu(p); /* IDLE tasks as never migrated */
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}
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#endif /* CONFIG_SMP */
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/*
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* Idle tasks are unconditionally rescheduled:
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*/
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static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p)
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{
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resched_task(rq->idle);
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}
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static struct task_struct *pick_next_task_idle(struct rq *rq)
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{
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schedstat_inc(rq, sched_goidle);
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return rq->idle;
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}
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/*
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* It is not legal to sleep in the idle task - print a warning
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* message if some code attempts to do it:
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*/
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static void
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dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep)
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|
{
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spin_unlock_irq(&rq->lock);
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printk(KERN_ERR "bad: scheduling from the idle thread!\n");
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dump_stack();
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spin_lock_irq(&rq->lock);
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}
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static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
|
|
|
|
{
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|
|
|
}
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|
#ifdef CONFIG_SMP
|
sched: simplify move_tasks()
The move_tasks() function is currently multiplexed with two distinct
capabilities:
1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.
The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.
The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.
This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()). However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:
1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.
One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list. This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.
Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).
NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.
[ mingo@elte.hu ]
this change also reduces code size nicely:
text data bss dec hex filename
39216 3618 24 42858 a76a sched.o.before
39173 3618 24 42815 a73f sched.o.after
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
18 years ago
|
|
|
static unsigned long
|
|
|
|
load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
|
|
unsigned long max_load_move,
|
|
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
|
|
int *all_pinned, int *this_best_prio)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
|
|
|
static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static void set_curr_task_idle(struct rq *rq)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static void switched_to_idle(struct rq *rq, struct task_struct *p,
|
|
|
|
int running)
|
|
|
|
{
|
|
|
|
/* Can this actually happen?? */
|
|
|
|
if (running)
|
|
|
|
resched_task(rq->curr);
|
|
|
|
else
|
|
|
|
check_preempt_curr(rq, p);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void prio_changed_idle(struct rq *rq, struct task_struct *p,
|
|
|
|
int oldprio, int running)
|
|
|
|
{
|
|
|
|
/* This can happen for hot plug CPUS */
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Reschedule if we are currently running on this runqueue and
|
|
|
|
* our priority decreased, or if we are not currently running on
|
|
|
|
* this runqueue and our priority is higher than the current's
|
|
|
|
*/
|
|
|
|
if (running) {
|
|
|
|
if (p->prio > oldprio)
|
|
|
|
resched_task(rq->curr);
|
|
|
|
} else
|
|
|
|
check_preempt_curr(rq, p);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Simple, special scheduling class for the per-CPU idle tasks:
|
|
|
|
*/
|
|
|
|
const struct sched_class idle_sched_class = {
|
|
|
|
/* .next is NULL */
|
|
|
|
/* no enqueue/yield_task for idle tasks */
|
|
|
|
|
|
|
|
/* dequeue is not valid, we print a debug message there: */
|
|
|
|
.dequeue_task = dequeue_task_idle,
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
.select_task_rq = select_task_rq_idle,
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
|
|
|
|
.check_preempt_curr = check_preempt_curr_idle,
|
|
|
|
|
|
|
|
.pick_next_task = pick_next_task_idle,
|
|
|
|
.put_prev_task = put_prev_task_idle,
|
|
|
|
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
.load_balance = load_balance_idle,
|
|
|
|
.move_one_task = move_one_task_idle,
|
|
|
|
#endif
|
|
|
|
|
|
|
|
.set_curr_task = set_curr_task_idle,
|
|
|
|
.task_tick = task_tick_idle,
|
|
|
|
|
|
|
|
.prio_changed = prio_changed_idle,
|
|
|
|
.switched_to = switched_to_idle,
|
|
|
|
|
|
|
|
/* no .task_new for idle tasks */
|
|
|
|
};
|