diff options
author | Morten Rasmussen <morten.rasmussen@arm.com> | 2016-01-13 16:38:52 +0000 |
---|---|---|
committer | Jon Medhurst <tixy@linaro.org> | 2016-04-13 11:42:02 +0100 |
commit | 742189403d6310da1bf62b6e5a3bbe27c911e76b (patch) | |
tree | ca5ad474ea0dbd6ad4581f01486e7521867dcc26 | |
parent | b94546683818ec93a0016b9e6f39d1175df3947f (diff) |
sched: Add group_misfit_task load-balance type
To maximize throughput in systems with reduced capacity cpus (e.g.
high RT/IRQ load and/or 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 that are scheduled on a reduced capacity
cpu need to be identified and migrated to a higher capacity cpu if
possible.
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 tasks that are not suitable for its
per-cpu capacity. group_misfit_task is only considered if the system is
not overloaded in any other way (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.
Change-Id: I092a348ed0ff37eae123f0d8d6dcf1435d51bfb1
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
-rw-r--r-- | kernel/sched/fair.c | 30 | ||||
-rw-r--r-- | kernel/sched/sched.h | 1 |
2 files changed, 24 insertions, 7 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5013abe3e79d..7b7414b67044 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5563,6 +5563,8 @@ again: if (hrtick_enabled(rq)) hrtick_start_fair(rq, p); + rq->misfit_task = !task_fits_max(p, rq->cpu); + return p; simple: cfs_rq = &rq->cfs; @@ -5584,9 +5586,13 @@ simple: if (hrtick_enabled(rq)) hrtick_start_fair(rq, p); + rq->misfit_task = !task_fits_max(p, rq->cpu); + return p; idle: + rq->misfit_task = 0; + new_tasks = idle_balance(rq); /* * Because idle_balance() releases (and re-acquires) rq->lock, it is @@ -5791,6 +5797,13 @@ 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 @@ -6288,12 +6301,6 @@ 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 */ @@ -6309,6 +6316,7 @@ struct sg_lb_stats { unsigned int group_weight; enum group_type group_type; int group_no_capacity; + int group_misfit_task; /* A cpu has a task too big for its capacity */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; unsigned int nr_preferred_running; @@ -6625,6 +6633,9 @@ static enum group_type group_classify(struct lb_env *env, if (sg_imbalanced(group)) return group_imbalanced; + if (sgs->group_misfit_task) + return group_misfit_task; + return group_other; } @@ -6676,8 +6687,11 @@ static inline void update_sg_lb_stats(struct lb_env *env, if (!nr_running && idle_cpu(i)) sgs->idle_cpus++; - if (cpu_overutilized(i)) + if (cpu_overutilized(i)) { *overutilized = true; + if (!sgs->group_misfit_task && rq->misfit_task) + sgs->group_misfit_task = capacity_of(i); + } } /* Adjust by relative CPU capacity of the group */ @@ -8259,6 +8273,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr))) rq->rd->overutilized = true; + + rq->misfit_task = !task_fits_max(curr, rq->cpu); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index bcf13796303b..c5d1981d17da 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -561,6 +561,7 @@ struct rq { #define CPU_LOAD_IDX_MAX 5 unsigned long cpu_load[CPU_LOAD_IDX_MAX]; unsigned long last_load_update_tick; + unsigned int misfit_task; #ifdef CONFIG_NO_HZ_COMMON u64 nohz_stamp; unsigned long nohz_flags; |