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SubjectRe: [PATCH] consolidate task preempts
Con Kolivas wrote:
> consolidate task preempts
>
>
>
> ------------------------------------------------------------------------
>
> TASK_PREEMPTS_CURR is only used when followed by resched_task. Consolidate
> the two into a single function.
>

I don't like the name.

I actually don't mind the code as it is now; it looks like it gets harder
to read, especially with that name.

Also, I think you might be better off to leave it inline, as it is just
a single comparison.

> Allow tasks of equal dynamic priority to preempt tasks of lower static
> priority.
>

Although this change makes the condition more complex. Is it really worth
doing?

> 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 2004-11-02 14:19:32.973509317 +1100
> +++ linux-2.6.10-rc1-mm2/kernel/sched.c 2004-11-02 14:26:23.444588405 +1100
> @@ -157,9 +157,6 @@
> (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
> (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
>
> -#define TASK_PREEMPTS_CURR(p, rq) \
> - ((p)->prio < (rq)->curr->prio)
> -
> /*
> * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
> * to time slice values: [800ms ... 100ms ... 5ms]
> @@ -810,6 +807,13 @@ inline int task_curr(const task_t *p)
> return cpu_curr(task_cpu(p)) == p;
> }
>
> +static void preempt(task_t *p, runqueue_t *rq)
> +{
> + if (p->prio < rq->curr->prio || (p->prio == rq->curr->prio &&
> + p->static_prio < rq->curr->static_prio))
> + resched_task(rq->curr);
> +}
> +
> #ifdef CONFIG_SMP
> enum request_type {
> REQ_MOVE_TASK,
> @@ -1106,10 +1110,8 @@ out_activate:
> * to be considered on this CPU.)
> */
> activate_task(p, rq, cpu == this_cpu);
> - if (!sync || cpu != this_cpu) {
> - if (TASK_PREEMPTS_CURR(p, rq))
> - resched_task(rq->curr);
> - }
> + if (!sync || cpu != this_cpu)
> + preempt(p, rq);
> success = 1;
>
> out_running:
> @@ -1263,8 +1265,7 @@ void fastcall wake_up_new_task(task_t *
> p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
> + rq->timestamp_last_tick;
> __activate_task(p, rq);
> - if (TASK_PREEMPTS_CURR(p, rq))
> - resched_task(rq->curr);
> + preempt(p, rq);
>
> schedstat_inc(rq, wunt_moved);
> /*
> @@ -1621,8 +1622,7 @@ void pull_task(runqueue_t *src_rq, prio_
> * Note that idle threads have a prio of MAX_PRIO, for this test
> * to be always true for them.
> */
> - if (TASK_PREEMPTS_CURR(p, this_rq))
> - resched_task(this_rq->curr);
> + preempt(p, this_rq);
> }
>
> /*
> @@ -3306,8 +3306,8 @@ recheck:
> if (task_running(rq, p)) {
> if (p->prio > oldprio)
> resched_task(rq->curr);
> - } else if (TASK_PREEMPTS_CURR(p, rq))
> - resched_task(rq->curr);
> + } else
> + preempt(p, rq);
> }
> task_rq_unlock(rq, &flags);
> out_unlock:
> @@ -4008,8 +4008,7 @@ static void __migrate_task(struct task_s
> + rq_dest->timestamp_last_tick;
> deactivate_task(p, rq_src);
> activate_task(p, rq_dest, 0);
> - if (TASK_PREEMPTS_CURR(p, rq_dest))
> - resched_task(rq_dest->curr);
> + preempt(p, rq_dest);
> }
>
> out:
>

-
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