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ANDROID: sched/rt: Add support for rt sync wakeups

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Some rt tasks undergo sync wakeup. Currently, these tasks will be placed
on other, often sleeping or otherwise idle CPUs, which can lead to
unnecessary power hits.

Bug: 157906395
Change-Id: I48864d0847bbe4f7813c842032880ad3f3b8b06b
Signed-off-by: J. Avila <elavila@google.com>
This commit is contained in:
J. Avila
2020-07-14 22:03:38 +00:00
parent 9a86bea7c3
commit da5f3cd378
3 changed files with 43 additions and 1 deletions
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3
kernel/sched/core.c
View File

@@ -2627,6 +2627,9 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
{
int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
if (wake_flags & WF_SYNC)
en_flags |= ENQUEUE_WAKEUP_SYNC;
lockdep_assert_held(&rq->lock);
if (p->sched_contributes_to_load)

39
kernel/sched/rt.c
View File

@@ -1372,6 +1372,27 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
enqueue_top_rt_rq(&rq->rt);
}
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
static inline bool should_honor_rt_sync(struct rq *rq, struct task_struct *p,
bool sync)
{
/*
* If the waker is CFS, then an RT sync wakeup would preempt the waker
* and force it to run for a likely small time after the RT wakee is
* done. So, only honor RT sync wakeups from RT wakers.
*/
return sync && task_has_rt_policy(rq->curr) &&
p->prio <= rq->rt.highest_prio.next &&
rq->rt.rt_nr_running <= 2;
}
#else
static inline bool should_honor_rt_sync(struct rq *rq, struct task_struct *p,
bool sync)
{
return 0;
}
#endif
/*
* Adding/removing a task to/from a priority array:
*/
@@ -1379,13 +1400,15 @@ static void
enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
{
struct sched_rt_entity *rt_se = &p->rt;
bool sync = !!(flags & ENQUEUE_WAKEUP_SYNC);
if (flags & ENQUEUE_WAKEUP)
rt_se->timeout = 0;
enqueue_rt_entity(rt_se, flags);
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
if (!task_current(rq, p) && p->nr_cpus_allowed > 1 &&
!should_honor_rt_sync(rq, p, sync))
enqueue_pushable_task(rq, p);
}
@@ -1462,9 +1485,12 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
{
struct task_struct *curr;
struct rq *rq;
struct rq *this_cpu_rq;
bool test;
int target_cpu = -1;
bool may_not_preempt;
bool sync = !!(flags & WF_SYNC);
int this_cpu;
trace_android_rvh_select_task_rq_rt(p, cpu, sd_flag,
flags, &target_cpu);
@@ -1479,6 +1505,8 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
rcu_read_lock();
curr = READ_ONCE(rq->curr); /* unlocked access */
this_cpu = smp_processor_id();
this_cpu_rq = cpu_rq(this_cpu);
/*
* If the current task on @p's runqueue is a softirq task,
@@ -1516,6 +1544,15 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
(unlikely(rt_task(curr)) &&
(curr->nr_cpus_allowed < 2 || curr->prio <= p->prio))));
/*
* Respect the sync flag as long as the task can run on this CPU.
*/
if (should_honor_rt_sync(this_cpu_rq, p, sync) &&
cpumask_test_cpu(this_cpu, p->cpus_ptr)) {
cpu = this_cpu;
goto out_unlock;
}
if (test || !rt_task_fits_capacity(p, cpu)) {
int target = find_lowest_rq(p);

2
kernel/sched/sched.h
View File

@@ -1785,6 +1785,8 @@ extern const u32 sched_prio_to_wmult[40];
#define ENQUEUE_MIGRATED 0x00
#endif
#define ENQUEUE_WAKEUP_SYNC 0x80
#define RETRY_TASK ((void *)-1UL)
struct sched_class {