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sched/fair: Favor higher cpus only for boosted tasks

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This CL separates the notion of boost and prefer_idle schedtune
attributes in cpu selection. Today only top-app
tasks are boosted. The CPU selection is slightly tweaked such that
higher order cpus are preferred only for boosted tasks (top-app) and the
rest would be skewed towards lower order cpus.
This avoids starvation issues for fg tasks when interacting with high
priority top-app tasks (a problem often seen in the case of system_server).

bug: 30245369
bug: 30292998
Change-Id: I0377e00893b9f6586eec55632a265518fd2fa8a1

Conflicts:
	kernel/sched/fair.c
This commit is contained in:
Srinath Sridharan 2016-07-29 17:50:11 +01:00 • committed by Amit Pundir
commit bfa1dd2bfd
1 changed files with 4 additions and 4 deletions
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8
kernel/sched/fair.c
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@ -5612,7 +5612,7 @@ done:
return target;
}
static inline int find_best_target(struct task_struct *p, bool prefer_idle)
static inline int find_best_target(struct task_struct *p, bool boosted, bool prefer_idle)
{
int iter_cpu;
int target_cpu = -1;
@ -5630,9 +5630,9 @@ static inline int find_best_target(struct task_struct *p, bool prefer_idle)
int idle_idx;
/*
* favor higher cpus for tasks that prefer idle cores
* Iterate from higher cpus for boosted tasks.
*/
int i = prefer_idle ? NR_CPUS-iter_cpu-1 : iter_cpu;
int i = boosted ? NR_CPUS-iter_cpu-1 : iter_cpu;
if (!cpu_online(i) || !cpumask_test_cpu(i, tsk_cpus_allowed(p)))
continue;
@ -5802,7 +5802,7 @@ static int energy_aware_wake_cpu(struct task_struct *p, int target, int sync)
bool boosted = 0;
bool prefer_idle = 0;
#endif
int tmp_target = find_best_target(p, boosted || prefer_idle);
int tmp_target = find_best_target(p, boosted, prefer_idle);
if (tmp_target >= 0) {
target_cpu = tmp_target;
if ((boosted || prefer_idle) && idle_cpu(target_cpu))