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HMP: Use unweighted load for hmp migration decisions

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Normal task and runqueue loading is scaled according to priority
to end up with a weighted load, known as the contribution.

We want the CPU time to be allotted according to priority, but
we also want to make big/little decisions based upon raw load.

It is common, for example, for Android apps following the dev
guide to end up with all their long-running or async action
threads as low priority unless they override the AsyncThread
constructor. All these threads are such low priority that they
become invisible to the hmp_offload routine.

Using unweighted load here allows us to maximise CPU usage in busy
situations.

Signed-off-by: Chris Redpath <chris.redpath@arm.com>
This commit is contained in:
Chris Redpath
2013-06-17 15:48:15 +01:00
committed by Jon Medhurst
parent 7362251d8a
commit ede58a69a3
1 changed files with 17 additions and 16 deletions
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33
kernel/sched/fair.c
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@@ -3841,20 +3841,24 @@ static inline unsigned int hmp_domain_min_load(struct hmp_domain *hmpd,
int *min_cpu)
{
int cpu;
int min_load = INT_MAX;
int min_cpu_temp = NR_CPUS;
int min_cpu_runnable_temp = NR_CPUS;
unsigned long min_runnable_load = INT_MAX;
unsigned long contrib;
for_each_cpu_mask(cpu, hmpd->cpus) {
if (cpu_rq(cpu)->cfs.tg_load_contrib < min_load) {
min_load = cpu_rq(cpu)->cfs.tg_load_contrib;
min_cpu_temp = cpu;
/* don't use the divisor in the loop, just at the end */
contrib = cpu_rq(cpu)->avg.runnable_avg_sum * scale_load_down(1024);
if (contrib < min_runnable_load) {
min_runnable_load = contrib;
min_cpu_runnable_temp = cpu;
}
}
if (min_cpu)
*min_cpu = min_cpu_temp;
*min_cpu = min_cpu_runnable_temp;
return min_load;
/* domain will often have at least one empty CPU */
return min_runnable_load ? min_runnable_load / (LOAD_AVG_MAX + 1) : 0;
}
/*
@@ -3882,22 +3886,18 @@ static inline unsigned int hmp_offload_down(int cpu, struct sched_entity *se)
return NR_CPUS;
/* Is the current domain fully loaded? */
/* load < ~94% */
/* load < ~50% */
min_usage = hmp_domain_min_load(hmp_cpu_domain(cpu), NULL);
if (min_usage < NICE_0_LOAD-64)
return NR_CPUS;
/* Is the cpu oversubscribed? */
/* load < ~194% */
if (cpu_rq(cpu)->cfs.tg_load_contrib < 2*NICE_0_LOAD-64)
if (min_usage < (NICE_0_LOAD>>1))
return NR_CPUS;
/* Is the task alone on the cpu? */
if (cpu_rq(cpu)->nr_running < 2)
if (cpu_rq(cpu)->cfs.nr_running < 2)
return NR_CPUS;
/* Is the task actually starving? */
if (hmp_task_starvation(se) > 768) /* <25% waiting */
/* >=25% ratio running/runnable = starving */
if (hmp_task_starvation(se) > 768)
return NR_CPUS;
/* Does the slower domain have spare cycles? */
@@ -3908,6 +3908,7 @@ static inline unsigned int hmp_offload_down(int cpu, struct sched_entity *se)
if (cpumask_test_cpu(dest_cpu, &hmp_slower_domain(cpu)->cpus))
return dest_cpu;
return NR_CPUS;
}
#endif /* CONFIG_SCHED_HMP */