Patch from Mike Galbraith <efault@gmx.de>
The change to activate_task() prevents sleepers from gaining too much
advantage from long sleeps. The change to deactivate_task() prevents tasks
with a high activation/deactivation rate from gaining permanent maximum bonus
points (irman's process load). The change to scheduler_tick() penalizes
interactive tasks who consume their timeslice such that they will be expired
quicker, and must re-earn their elevated status. This "cures" all of the
starvation problems I've seen here.
kernel/sched.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletion(-)
diff -puN kernel/sched.c~scheduler-starvation-fixes kernel/sched.c
--- 25/kernel/sched.c~scheduler-starvation-fixes 2003-03-15 00:05:48.000000000 -0800
+++ 25-akpm/kernel/sched.c 2003-03-15 00:05:48.000000000 -0800
@@ -75,7 +75,7 @@ int exit_weight = 3;
int prio_bonus_ratio = 25;
int interactive_delta = 2;
int max_sleep_avg = 10 * HZ;
-int starvation_limit = 10 * HZ;
+int starvation_limit = 2 * (200 * HZ) / 1000;
int node_threshold = 125;
#define MIN_TIMESLICE (min_timeslice)
@@ -370,6 +370,8 @@ static inline int activate_task(task_t *
* spends sleeping, the higher the average gets - and the
* higher the priority boost gets as well.
*/
+ if (sleep_time > MAX_TIMESLICE)
+ sleep_time = MAX_TIMESLICE;
sleep_avg = p->sleep_avg + sleep_time;
/*
@@ -411,6 +413,8 @@ static inline void deactivate_task(struc
rq->nr_uninterruptible++;
dequeue_task(p, p->array);
p->array = NULL;
+ if (p->sleep_avg)
+ p->sleep_avg--;
}
/*
@@ -1263,6 +1267,8 @@ void scheduler_tick(int user_ticks, int
if (!--p->time_slice) {
dequeue_task(p, rq->active);
set_tsk_need_resched(p);
+ if (TASK_INTERACTIVE(p) && p->sleep_avg > MIN_TIMESLICE)
+ p->sleep_avg -= MIN_TIMESLICE;
p->prio = effective_prio(p);
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
_