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author | 2018-07-04 11:17:40 +0100 | |
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committer | 2018-09-10 11:05:49 +0200 | |
commit | 3b1baa6496e6b7ad016342a9d256bdfb072ce902 (patch) | |
tree | 9e91be8d2548ed6113f0e69636c5e22766d0b8c5 /kernel/sched | |
parent | sched/topology: Add static_key for asymmetric CPU capacity optimizations (diff) | |
download | linux-3b1baa6496e6b7ad016342a9d256bdfb072ce902.tar.gz linux-3b1baa6496e6b7ad016342a9d256bdfb072ce902.tar.bz2 linux-3b1baa6496e6b7ad016342a9d256bdfb072ce902.zip |
sched/fair: Add 'group_misfit_task' load-balance type
To maximize throughput in systems with asymmetric CPU capacities (e.g.
ARM big.LITTLE) load-balancing has to consider task and CPU utilization
as well as per-CPU compute capacity when load-balancing in addition to
the current average load based load-balancing policy. Tasks with high
utilization that are scheduled on a lower capacity CPU need to be
identified and migrated to a higher capacity CPU if possible to maximize
throughput.
To implement this additional policy an additional group_type
(load-balance scenario) is added: 'group_misfit_task'. This represents
scenarios where a sched_group has one or more tasks that are not
suitable for its per-CPU capacity. 'group_misfit_task' is only considered
if the system is not overloaded or imbalanced ('group_imbalanced' or
'group_overloaded').
Identifying misfit tasks requires the rq lock to be held. To avoid
taking remote rq locks to examine source sched_groups for misfit tasks,
each CPU is responsible for tracking misfit tasks themselves and update
the rq->misfit_task flag. This means checking task utilization when
tasks are scheduled and on sched_tick.
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: gaku.inami.xh@renesas.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1530699470-29808-3-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/fair.c | 54 | ||||
-rw-r--r-- | kernel/sched/sched.h | 2 |
2 files changed, 48 insertions, 8 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3e5071aeb117..6e04bea5b11a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -693,6 +693,7 @@ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); static unsigned long task_h_load(struct task_struct *p); +static unsigned long capacity_of(int cpu); /* Give new sched_entity start runnable values to heavy its load in infant time */ void init_entity_runnable_average(struct sched_entity *se) @@ -1446,7 +1447,6 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, static unsigned long weighted_cpuload(struct rq *rq); static unsigned long source_load(int cpu, int type); static unsigned long target_load(int cpu, int type); -static unsigned long capacity_of(int cpu); /* Cached statistics for all CPUs within a node */ struct numa_stats { @@ -3647,6 +3647,29 @@ util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) WRITE_ONCE(p->se.avg.util_est, ue); } +static inline int task_fits_capacity(struct task_struct *p, long capacity) +{ + return capacity * 1024 > task_util_est(p) * capacity_margin; +} + +static inline void update_misfit_status(struct task_struct *p, struct rq *rq) +{ + if (!static_branch_unlikely(&sched_asym_cpucapacity)) + return; + + if (!p) { + rq->misfit_task_load = 0; + return; + } + + if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) { + rq->misfit_task_load = 0; + return; + } + + rq->misfit_task_load = task_h_load(p); +} + #else /* CONFIG_SMP */ #define UPDATE_TG 0x0 @@ -3676,6 +3699,7 @@ util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {} static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) {} +static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {} #endif /* CONFIG_SMP */ @@ -6201,7 +6225,7 @@ static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) /* Bring task utilization in sync with prev_cpu */ sync_entity_load_avg(&p->se); - return min_cap * 1024 < task_util(p) * capacity_margin; + return !task_fits_capacity(p, min_cap); } /* @@ -6618,9 +6642,12 @@ done: __maybe_unused; if (hrtick_enabled(rq)) hrtick_start_fair(rq, p); + update_misfit_status(p, rq); + return p; idle: + update_misfit_status(NULL, rq); new_tasks = idle_balance(rq, rf); /* @@ -6826,6 +6853,13 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10; enum fbq_type { regular, remote, all }; +enum group_type { + group_other = 0, + group_misfit_task, + group_imbalanced, + group_overloaded, +}; + #define LBF_ALL_PINNED 0x01 #define LBF_NEED_BREAK 0x02 #define LBF_DST_PINNED 0x04 @@ -7399,12 +7433,6 @@ static unsigned long task_h_load(struct task_struct *p) /********** Helpers for find_busiest_group ************************/ -enum group_type { - group_other = 0, - group_imbalanced, - group_overloaded, -}; - /* * sg_lb_stats - stats of a sched_group required for load_balancing */ @@ -7420,6 +7448,7 @@ struct sg_lb_stats { unsigned int group_weight; enum group_type group_type; int group_no_capacity; + unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; unsigned int nr_preferred_running; @@ -7712,6 +7741,9 @@ group_type group_classify(struct sched_group *group, if (sg_imbalanced(group)) return group_imbalanced; + if (sgs->group_misfit_task_load) + return group_misfit_task; + return group_other; } @@ -7786,6 +7818,10 @@ static inline void update_sg_lb_stats(struct lb_env *env, */ if (!nr_running && idle_cpu(i)) sgs->idle_cpus++; + + if (env->sd->flags & SD_ASYM_CPUCAPACITY && + sgs->group_misfit_task_load < rq->misfit_task_load) + sgs->group_misfit_task_load = rq->misfit_task_load; } /* Adjust by relative CPU capacity of the group */ @@ -9567,6 +9603,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) if (static_branch_unlikely(&sched_numa_balancing)) task_tick_numa(rq, curr); + + update_misfit_status(curr, rq); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 0f36adc31ba5..7dbf67d147a2 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -842,6 +842,8 @@ struct rq { unsigned char idle_balance; + unsigned long misfit_task_load; + /* For active balancing */ int active_balance; int push_cpu; |