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sched/fair: Add sched_group per-CPU max capacity 

The current sg->min_capacity tracks the lowest per-CPU compute capacity
available in the sched_group when rt/irq pressure is taken into account.
Minimum capacity isn't the ideal metric for tracking if a sched_group
needs offloading to another sched_group for some scenarios, e.g. a
sched_group with multiple CPUs if only one is under heavy pressure.
Tracking maximum capacity isn't perfect either but a better choice for
some situations as it indicates that the sched_group definitely compute
capacity constrained either due to rt/irq pressure on all CPUs or
asymmetric CPU capacities (e.g. big.LITTLE).

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/1530699470-29808-4-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Morten Rasmussen 2018-07-04 11:17:41 +01:00 committed by Ingo Molnar
parent 3b1baa6496
commit e3d6d0cb66
3 changed files with 23 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
kernel/sched/fair.c
View File

@ -7557,13 +7557,14 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
cpu_rq(cpu)->cpu_capacity = capacity;
sdg->sgc->capacity = capacity;
sdg->sgc->min_capacity = capacity;
sdg->sgc->max_capacity = capacity;
}
void update_group_capacity(struct sched_domain *sd, int cpu)
{
struct sched_domain *child = sd->child;
struct sched_group *group, *sdg = sd->groups;
unsigned long capacity, min_capacity;
unsigned long capacity, min_capacity, max_capacity;
unsigned long interval;
interval = msecs_to_jiffies(sd->balance_interval);
@ -7577,6 +7578,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
capacity = 0;
min_capacity = ULONG_MAX;
max_capacity = 0;
if (child->flags & SD_OVERLAP) {
/*
@ -7607,6 +7609,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
}
min_capacity = min(capacity, min_capacity);
max_capacity = max(capacity, max_capacity);
}
} else {
/*
@ -7620,12 +7623,14 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
capacity += sgc->capacity;
min_capacity = min(sgc->min_capacity, min_capacity);
max_capacity = max(sgc->max_capacity, max_capacity);
group = group->next;
} while (group != child->groups);
}
sdg->sgc->capacity = capacity;
sdg->sgc->min_capacity = min_capacity;
sdg->sgc->max_capacity = max_capacity;
}
/*
@ -7721,16 +7726,27 @@ group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
}
/*
* group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
* group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
* per-CPU capacity than sched_group ref.
*/
static inline bool
group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
return sg->sgc->min_capacity * capacity_margin <
ref->sgc->min_capacity * 1024;
}
/*
* group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
* per-CPU capacity_orig than sched_group ref.
*/
static inline bool
group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
return sg->sgc->max_capacity * capacity_margin <
ref->sgc->max_capacity * 1024;
}
static inline enum
group_type group_classify(struct sched_group *group,
struct sg_lb_stats *sgs)
@ -7876,7 +7892,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
* power/energy consequences are not considered.
*/
if (sgs->sum_nr_running <= sgs->group_weight &&
group_smaller_cpu_capacity(sds->local, sg))
group_smaller_min_cpu_capacity(sds->local, sg))
return false;
asym_packing:

1
kernel/sched/sched.h
View File

@ -1197,6 +1197,7 @@ struct sched_group_capacity {
*/
unsigned long capacity;
unsigned long min_capacity; /* Min per-CPU capacity in group */
unsigned long max_capacity; /* Max per-CPU capacity in group */
unsigned long next_update;
int imbalance; /* XXX unrelated to capacity but shared group state */

2
kernel/sched/topology.c
View File

@ -693,6 +693,7 @@ static void init_overlap_sched_group(struct sched_domain *sd,
sg_span = sched_group_span(sg);
sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
}
static int
@ -852,6 +853,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sched_group_span(sg));
sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
return sg;
}