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sched/walt: avoid halted cpus for rt in find_lowest_rq

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select_task_rq_rt() and push_rt_task() need to select
a cpu, and ultimately attempt to get a good match on
a cpu through find_lowest_rq. Walt hooks into this
routine to make an adjustment such that the best energy
aware cpu is found.

It is possible that walt_rt_energy_aware_wake_cpu will be
unable to find a non-halted cpu. find_lowest_rq at that
point will use the lowest_mask, initialized from the
task cpus_ptr, to find a CPU. At this point, find_lowest_rq
might return a halted CPU.

Instead, in the case where walt cannot find a best cpu to
choose, force the lowest_mask to no longer include halted
cpus, which will push find_lowest_rq to no longer choose a
halted cpu. In the unlikely event that find_lowest_rq still
fails to find a cpu it will pick anything from the
lowest_mask. In the unlikely event that lowest_mask is empty
after removing all of the halted cpus, find_lowest_rq will
fail and the cpu chosen will be unconstrained by halt.

Change-Id: I398bc804eb474396f6f06e2c3d4308fea71dafe8
Signed-off-by: Stephen Dickey <quic_dickey@quicinc.com>
This commit is contained in:
Stephen Dickey 2021-11-12 16:27:23 -08:00 committed by Rishabh Bhatnagar
parent dcbd6c7246
commit 612b4f86c1
1 changed files with 20 additions and 4 deletions
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24
kernel/sched/walt/walt_rt.c
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@ -10,8 +10,8 @@
static DEFINE_PER_CPU(cpumask_var_t, walt_local_cpu_mask);
static void walt_rt_energy_aware_wake_cpu(void *unused, struct task_struct *task,
struct cpumask *lowest_mask, int ret, int *best_cpu)
static void walt_rt_energy_aware_wake_cpu(struct task_struct *task, struct cpumask *lowest_mask,
int ret, int *best_cpu)
{
int cpu;
unsigned long util, best_cpu_util = ULONG_MAX;
@ -205,7 +205,7 @@ static void walt_select_task_rq_rt(void *unused, struct task_struct *task, int c
ret = cpupri_find_fitness(&task_rq(task)->rd->cpupri, task,
lowest_mask, walt_rt_task_fits_capacity);
walt_rt_energy_aware_wake_cpu(NULL, task, lowest_mask, ret, &target);
walt_rt_energy_aware_wake_cpu(task, lowest_mask, ret, &target);
/*
* If cpu is non-preemptible, prefer remote cpu
@ -220,6 +220,22 @@ static void walt_select_task_rq_rt(void *unused, struct task_struct *task, int c
rcu_read_unlock();
}
static void walt_rt_find_lowest_rq(void *unused, struct task_struct *task,
struct cpumask *lowest_mask, int ret, int *best_cpu)
{
walt_rt_energy_aware_wake_cpu(task, lowest_mask, ret, best_cpu);
/*
* Walt was not able to find a non-halted best cpu. Ensure that
* find_lowest_rq doesn't use a halted cpu going forward, but
* does a best effort itself to find a good CPU.
*/
if (*best_cpu == -1)
cpumask_andnot(lowest_mask, lowest_mask, cpu_halt_mask);
}
void walt_rt_init(void)
{
unsigned int i;
@ -233,5 +249,5 @@ void walt_rt_init(void)
}
register_trace_android_rvh_select_task_rq_rt(walt_select_task_rq_rt, NULL);
register_trace_android_rvh_find_lowest_rq(walt_rt_energy_aware_wake_cpu, NULL);
register_trace_android_rvh_find_lowest_rq(walt_rt_find_lowest_rq, NULL);
}