diff options
author | Morten Rasmussen <Morten.Rasmussen@arm.com> | 2012-09-14 14:38:09 +0100 |
---|---|---|
committer | Jon Medhurst <tixy@linaro.org> | 2013-07-17 11:12:24 +0100 |
commit | 798e82cab1a39f4d75796be024c4d7b08bc062e8 (patch) | |
tree | d98e5158520aa6cc1333ffeaf5d7f15aaa8658c5 /kernel | |
parent | be6ef1d56e70bfdfd79174d7d23a4b12d5b911ee (diff) |
sched: Task placement for heterogeneous systems based on task load-tracking
This patch introduces the basic SCHED_HMP infrastructure. Each class of
cpus is represented by a hmp_domain and tasks will only be moved between
these domains when their load profiles suggest it is beneficial.
SCHED_HMP relies heavily on the task load-tracking introduced in Paul
Turners fair group scheduling patch set:
<https://lkml.org/lkml/2012/8/23/267>
SCHED_HMP requires that the platform implements arch_get_hmp_domains()
which should set up the platform specific list of hmp_domains. It is
also assumed that the platform disables SD_LOAD_BALANCE for the
appropriate sched_domains.
Tasks placement takes place every time a task is to be inserted into
a runqueue based on its load history. The task placement decision is
based on load thresholds.
There are no restrictions on the number of hmp_domains, however,
multiple (>2) has not been tested and the up/down migration policy is
rather simple.
Signed-off-by: Morten Rasmussen <Morten.Rasmussen@arm.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched/fair.c | 168 | ||||
-rw-r--r-- | kernel/sched/sched.h | 6 |
2 files changed, 174 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e6db20a013b..7d192bd8242 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3340,6 +3340,125 @@ done: return target; } +#ifdef CONFIG_SCHED_HMP +/* + * Heterogenous multiprocessor (HMP) optimizations + * + * The cpu types are distinguished using a list of hmp_domains + * which each represent one cpu type using a cpumask. + * The list is assumed ordered by compute capacity with the + * fastest domain first. + */ +DEFINE_PER_CPU(struct hmp_domain *, hmp_cpu_domain); + +extern void __init arch_get_hmp_domains(struct list_head *hmp_domains_list); + +/* Setup hmp_domains */ +static int __init hmp_cpu_mask_setup(void) +{ + char buf[64]; + struct hmp_domain *domain; + struct list_head *pos; + int dc, cpu; + + pr_debug("Initializing HMP scheduler:\n"); + + /* Initialize hmp_domains using platform code */ + arch_get_hmp_domains(&hmp_domains); + if (list_empty(&hmp_domains)) { + pr_debug("HMP domain list is empty!\n"); + return 0; + } + + /* Print hmp_domains */ + dc = 0; + list_for_each(pos, &hmp_domains) { + domain = list_entry(pos, struct hmp_domain, hmp_domains); + cpulist_scnprintf(buf, 64, &domain->cpus); + pr_debug(" HMP domain %d: %s\n", dc, buf); + + for_each_cpu_mask(cpu, domain->cpus) { + per_cpu(hmp_cpu_domain, cpu) = domain; + } + dc++; + } + + return 1; +} + +/* + * Migration thresholds should be in the range [0..1023] + * hmp_up_threshold: min. load required for migrating tasks to a faster cpu + * hmp_down_threshold: max. load allowed for tasks migrating to a slower cpu + * The default values (512, 256) offer good responsiveness, but may need + * tweaking suit particular needs. + */ +unsigned int hmp_up_threshold = 512; +unsigned int hmp_down_threshold = 256; + +static unsigned int hmp_up_migration(int cpu, struct sched_entity *se); +static unsigned int hmp_down_migration(int cpu, struct sched_entity *se); + +/* Check if cpu is in fastest hmp_domain */ +static inline unsigned int hmp_cpu_is_fastest(int cpu) +{ + struct list_head *pos; + + pos = &hmp_cpu_domain(cpu)->hmp_domains; + return pos == hmp_domains.next; +} + +/* Check if cpu is in slowest hmp_domain */ +static inline unsigned int hmp_cpu_is_slowest(int cpu) +{ + struct list_head *pos; + + pos = &hmp_cpu_domain(cpu)->hmp_domains; + return list_is_last(pos, &hmp_domains); +} + +/* Next (slower) hmp_domain relative to cpu */ +static inline struct hmp_domain *hmp_slower_domain(int cpu) +{ + struct list_head *pos; + + pos = &hmp_cpu_domain(cpu)->hmp_domains; + return list_entry(pos->next, struct hmp_domain, hmp_domains); +} + +/* Previous (faster) hmp_domain relative to cpu */ +static inline struct hmp_domain *hmp_faster_domain(int cpu) +{ + struct list_head *pos; + + pos = &hmp_cpu_domain(cpu)->hmp_domains; + return list_entry(pos->prev, struct hmp_domain, hmp_domains); +} + +/* + * Selects a cpu in previous (faster) hmp_domain + * Note that cpumask_any_and() returns the first cpu in the cpumask + */ +static inline unsigned int hmp_select_faster_cpu(struct task_struct *tsk, + int cpu) +{ + return cpumask_any_and(&hmp_faster_domain(cpu)->cpus, + tsk_cpus_allowed(tsk)); +} + +/* + * Selects a cpu in next (slower) hmp_domain + * Note that cpumask_any_and() returns the first cpu in the cpumask + */ +static inline unsigned int hmp_select_slower_cpu(struct task_struct *tsk, + int cpu) +{ + return cpumask_any_and(&hmp_slower_domain(cpu)->cpus, + tsk_cpus_allowed(tsk)); +} + +#endif /* CONFIG_SCHED_HMP */ + /* * sched_balance_self: balance the current task (running on cpu) in domains * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and @@ -3438,6 +3557,16 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) unlock: rcu_read_unlock(); +#ifdef CONFIG_SCHED_HMP + if (hmp_up_migration(prev_cpu, &p->se)) + return hmp_select_faster_cpu(p, prev_cpu); + if (hmp_down_migration(prev_cpu, &p->se)) + return hmp_select_slower_cpu(p, prev_cpu); + /* Make sure that the task stays in its previous hmp domain */ + if (!cpumask_test_cpu(new_cpu, &hmp_cpu_domain(prev_cpu)->cpus)) + return prev_cpu; +#endif + return new_cpu; } @@ -5708,6 +5837,41 @@ need_kick: static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { } #endif +#ifdef CONFIG_SCHED_HMP +/* Check if task should migrate to a faster cpu */ +static unsigned int hmp_up_migration(int cpu, struct sched_entity *se) +{ + struct task_struct *p = task_of(se); + + if (hmp_cpu_is_fastest(cpu)) + return 0; + + if (cpumask_intersects(&hmp_faster_domain(cpu)->cpus, + tsk_cpus_allowed(p)) + && se->avg.load_avg_ratio > hmp_up_threshold) { + return 1; + } + return 0; +} + +/* Check if task should migrate to a slower cpu */ +static unsigned int hmp_down_migration(int cpu, struct sched_entity *se) +{ + struct task_struct *p = task_of(se); + + if (hmp_cpu_is_slowest(cpu)) + return 0; + + if (cpumask_intersects(&hmp_slower_domain(cpu)->cpus, + tsk_cpus_allowed(p)) + && se->avg.load_avg_ratio < hmp_down_threshold) { + return 1; + } + return 0; +} + +#endif /* CONFIG_SCHED_HMP */ + /* * run_rebalance_domains is triggered when needed from the scheduler tick. * Also triggered for nohz idle balancing (with nohz_balancing_kick set). @@ -6218,6 +6382,10 @@ __init void init_sched_fair_class(void) zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); cpu_notifier(sched_ilb_notifier, 0); #endif + +#ifdef CONFIG_SCHED_HMP + hmp_cpu_mask_setup(); +#endif #endif /* SMP */ } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index e1d155c68df..2e90c98900d 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -642,6 +642,12 @@ static inline unsigned int group_first_cpu(struct sched_group *group) extern int group_balance_cpu(struct sched_group *sg); +#ifdef CONFIG_SCHED_HMP +static LIST_HEAD(hmp_domains); +DECLARE_PER_CPU(struct hmp_domain *, hmp_cpu_domain); +#define hmp_cpu_domain(cpu) (per_cpu(hmp_cpu_domain, (cpu))) +#endif /* CONFIG_SCHED_HMP */ + #endif /* CONFIG_SMP */ #include "stats.h" |