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sched: add preference for prev and sibling CPU in HMP task placement

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At present HMP task placement algorithm places wake-up task on any lowest
power cost CPU in the system even if the task's previous CPU is also one
of the lowest power cost CPU.  Placing task on the previous CPU can reduce
cache bouncing.

Add a bias towards the task's previous CPU and CPU in the same cache domain
with previous CPU.

Change-Id: Ieab3840432e277048058da76764b3a3f16e20c56
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
This commit is contained in:
Joonwoo Park 2015-08-11 15:35:02 -07:00 • committed by David Keitel
parent 8623286277
commit 44af3b5e03
1 changed files with 22 additions and 8 deletions
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30
kernel/sched/fair.c
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@ -3182,9 +3182,9 @@ static int select_best_cpu(struct task_struct *p, int target, int reason,
int sync)
{
int i, best_cpu = -1, best_idle_cpu = -1, best_capacity_cpu = -1;
int prev_cpu = task_cpu(p);
int cpu_cost, min_cost = INT_MAX;
u64 tload, cpu_load;
int prev_cpu = task_cpu(p), best_sibling_cpu = -1;
int cpu_cost, min_cost = INT_MAX, best_sibling_cpu_cost = INT_MAX;
u64 tload, cpu_load, best_sibling_cpu_load = ULLONG_MAX;
u64 min_load = ULLONG_MAX;
s64 spare_capacity, highest_spare_capacity = 0;
int boost = sched_boost();
@ -3238,21 +3238,32 @@ static int select_best_cpu(struct task_struct *p, int target, int reason,
cpu_cost = power_cost(tload + cpu_load, i);
if (cpu_cost > min_cost)
continue;
/*
* If the task fits in a CPU in a lower power band, that
* overrides all other considerations.
*/
if (power_delta_exceeded(cpu_cost, min_cost)) {
if (cpu_cost > min_cost)
continue;
min_cost = cpu_cost;
min_load = ULLONG_MAX;
best_cpu = -1;
}
if (cpu_cost < min_cost ||
(cpu_cost == min_cost && cpu_load < min_load)) {
if (i != prev_cpu && cpus_share_cache(prev_cpu, i)) {
if (best_sibling_cpu_cost > cpu_cost ||
(best_sibling_cpu_cost == cpu_cost &&
best_sibling_cpu_load > cpu_load)) {
best_sibling_cpu_cost = cpu_cost;
best_sibling_cpu_load = cpu_load;
best_sibling_cpu = i;
}
}
if ((cpu_cost < min_cost) ||
((best_cpu != prev_cpu && min_load > cpu_load) ||
i == prev_cpu)) {
if (need_idle) {
if (idle_cpu(i)) {
min_cost = cpu_cost;
@ -3274,6 +3285,9 @@ static int select_best_cpu(struct task_struct *p, int target, int reason,
best_cpu = prev_cpu;
else
best_cpu = best_capacity_cpu;
} else {
if (best_cpu != prev_cpu && min_cost == best_sibling_cpu_cost)
best_cpu = best_sibling_cpu;
}
trace_sched_task_load(p, boost, reason, sync, need_idle);