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sched: rework wakeup preemption 

Rework the wakeup preemption to work on real runtime instead of
the virtual runtime. This greatly simplifies the code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
wifi-calibration
Peter Zijlstra 2008-09-23 14:54:23 +02:00 committed by Ingo Molnar
parent 1a73ef6ac3
commit 6956985009
1 changed files with 4 additions and 129 deletions
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133
kernel/sched_fair.c
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@ -408,64 +408,6 @@ static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
return __sched_period(nr_running);
}
/*
* The goal of calc_delta_asym() is to be asymmetrically around NICE_0_LOAD, in
* that it favours >=0 over <0.
*
* -20 |
* |
* 0 --------+-------
* .'
* 19 .'
*
*/
static unsigned long
calc_delta_asym(unsigned long delta, struct sched_entity *se)
{
struct load_weight lw = {
.weight = NICE_0_LOAD,
.inv_weight = 1UL << (WMULT_SHIFT-NICE_0_SHIFT)
};
for_each_sched_entity(se) {
struct load_weight *se_lw = &se->load;
unsigned long rw = cfs_rq_of(se)->load.weight;
#ifdef CONFIG_FAIR_SCHED_GROUP
struct cfs_rq *cfs_rq = se->my_q;
struct task_group *tg = NULL
if (cfs_rq)
tg = cfs_rq->tg;
if (tg && tg->shares < NICE_0_LOAD) {
/*
* scale shares to what it would have been had
* tg->weight been NICE_0_LOAD:
*
* weight = 1024 * shares / tg->weight
*/
lw.weight *= se->load.weight;
lw.weight /= tg->shares;
lw.inv_weight = 0;
se_lw = &lw;
rw += lw.weight - se->load.weight;
} else
#endif
if (se->load.weight < NICE_0_LOAD) {
se_lw = &lw;
rw += NICE_0_LOAD - se->load.weight;
}
delta = calc_delta_mine(delta, rw, se_lw);
}
return delta;
}
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
@ -1281,53 +1223,11 @@ static unsigned long wakeup_gran(struct sched_entity *se)
* + nice tasks.
*/
if (sched_feat(ASYM_GRAN))
gran = calc_delta_asym(sysctl_sched_wakeup_granularity, se);
else
gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);
gran = calc_delta_mine(gran, NICE_0_LOAD, &se->load);
return gran;
}
/*
* Should 'se' preempt 'curr'.
*
* |s1
* |s2
* |s3
* g
* |<--->|c
*
* w(c, s1) = -1
* w(c, s2) = 0
* w(c, s3) = 1
*
*/
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
s64 gran, vdiff = curr->vruntime - se->vruntime;
if (vdiff < 0)
return -1;
gran = wakeup_gran(curr);
if (vdiff > gran)
return 1;
return 0;
}
/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
int depth = 0;
for_each_sched_entity(se)
depth++;
return depth;
}
/*
* Preempt the current task with a newly woken task if needed:
*/
@ -1336,7 +1236,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se, *pse = &p->se;
int se_depth, pse_depth;
s64 delta_exec;
if (unlikely(rt_prio(p->prio))) {
update_rq_clock(rq);
@ -1374,33 +1274,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
return;
}
/*
* preemption test can be made between sibling entities who are in the
* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
* both tasks until we find their ancestors who are siblings of common
* parent.
*/
/* First walk up until both entities are at same depth */
se_depth = depth_se(se);
pse_depth = depth_se(pse);
while (se_depth > pse_depth) {
se_depth--;
se = parent_entity(se);
}
while (pse_depth > se_depth) {
pse_depth--;
pse = parent_entity(pse);
}
while (!is_same_group(se, pse)) {
se = parent_entity(se);
pse = parent_entity(pse);
}
if (wakeup_preempt_entity(se, pse) == 1)
delta_exec = se->sum_exec_runtime - se->prev_sum_exec_runtime;
if (delta_exec > wakeup_gran(pse))
resched_task(curr);
}