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sched/fair: refactor find_best_target() for simplicity

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Simplify backup_capacity handling and use 'unsigned long'
data type for cpu capacity, simplify target_util handling,
simplify idle_idx handling & refactor min_util, new_util.

Also return first idle cpu for prefer_idle task immediately.

Change-Id: Ic89e140f7b369f3965703fdc8463013d16e9b94a
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
This commit is contained in:
Dietmar Eggemann 2017-01-07 14:33:51 +00:00 • committed by Andres Oportus
parent d3f5e8c3e9
commit b31ae71ef7
1 changed files with 20 additions and 40 deletions
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60
kernel/sched/fair.c
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@ -5756,13 +5756,12 @@ static int start_cpu(bool boosted)
static inline int find_best_target(struct task_struct *p, bool boosted, bool prefer_idle)
{
int target_cpu = -1;
int target_util = 0;
int backup_capacity = 0;
unsigned long target_util = prefer_idle ? ULONG_MAX : 0;
unsigned long backup_capacity = ULONG_MAX;
int best_idle_cpu = -1;
int best_idle_cstate = INT_MAX;
int backup_cpu = -1;
unsigned long min_util;
unsigned long new_util;
unsigned long min_util = boosted_task_util(p);
struct sched_domain *sd;
struct sched_group *sg;
int cpu = start_cpu(boosted);
@ -5777,15 +5776,11 @@ static inline int find_best_target(struct task_struct *p, bool boosted, bool pre
sg = sd->groups;
min_util = boosted_task_util(p);
do {
int i;
for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg)) {
int cur_capacity;
struct rq *rq;
int idle_idx;
unsigned long cur_capacity, new_util;
if (!cpu_online(i))
continue;
@ -5803,6 +5798,7 @@ static inline int find_best_target(struct task_struct *p, bool boosted, bool pre
* than the one required to boost the task.
*/
new_util = max(min_util, new_util);
if (new_util > capacity_orig_of(i))
continue;
@ -5815,38 +5811,25 @@ static inline int find_best_target(struct task_struct *p, bool boosted, bool pre
* Unconditionally favoring tasks that prefer idle cpus to
* improve latency.
*/
if (idle_cpu(i) && prefer_idle) {
if (best_idle_cpu < 0)
best_idle_cpu = i;
continue;
}
if (idle_cpu(i) && prefer_idle)
return i;
cur_capacity = capacity_curr_of(i);
rq = cpu_rq(i);
idle_idx = idle_get_state_idx(rq);
if (new_util < cur_capacity) {
if (cpu_rq(i)->nr_running) {
if (!prefer_idle) {
/* Find a target cpu with highest
* utilization.
*/
if (target_util == 0 ||
target_util < new_util) {
target_cpu = i;
target_util = new_util;
}
} else {
/* Find a target cpu with lowest
* utilization.
*/
if (target_util == 0 ||
target_util > new_util) {
target_cpu = i;
target_util = new_util;
}
/*
* Find a target cpu with the lowest/highest
* utilization if prefer_idle/!prefer_idle.
*/
if ((prefer_idle && target_util > new_util) ||
(!prefer_idle && target_util < new_util)) {
target_util = new_util;
target_cpu = i;
}
} else if (!prefer_idle) {
int idle_idx = idle_get_state_idx(cpu_rq(i));
if (best_idle_cpu < 0 ||
(sysctl_sched_cstate_aware &&
best_idle_cstate > idle_idx)) {
@ -5854,18 +5837,15 @@ static inline int find_best_target(struct task_struct *p, bool boosted, bool pre
best_idle_cpu = i;
}
}
} else if (backup_capacity == 0 ||
backup_capacity > cur_capacity) {
// Find a backup cpu with least capacity.
} else if (backup_capacity > cur_capacity) {
/* Find a backup cpu with least capacity. */
backup_capacity = cur_capacity;
backup_cpu = i;
}
}
} while (sg = sg->next, sg != sd->groups);
if (prefer_idle && best_idle_cpu >= 0)
target_cpu = best_idle_cpu;
else if (target_cpu < 0)
if (target_cpu < 0)
target_cpu = best_idle_cpu >= 0 ? best_idle_cpu : backup_cpu;
return target_cpu;