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Subject[PATCH v2 04/11] sched: unify imbalance bias for target group
Date
Old code considers the bias in source/target_load already. but still
use imbalance_pct as last check in idlest/busiest group finding. It is
also a kind of redundant job. If we bias imbalance in source/target_load,
we'd better not use imbalance_pct again.

After cpu_load array removed, it is nice time to unify the target bias
consideration. So I remove the imbalance_pct from last check and add the
live bias using.

Signed-off-by: Alex Shi <alex.shi@linaro.org>
---
kernel/sched/fair.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index eeffe75..a85a10b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1016,7 +1016,7 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page,

static unsigned long weighted_cpuload(const int cpu);
static unsigned long source_load(int cpu);
-static unsigned long target_load(int cpu);
+static unsigned long target_load(int cpu, int imbalance_pct);
static unsigned long power_of(int cpu);
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

@@ -3967,7 +3967,7 @@ static unsigned long source_load(int cpu)
* Return a high guess at the load of a migration-target cpu weighted
* according to the scheduling class and "nice" value.
*/
-static unsigned long target_load(int cpu)
+static unsigned long target_load(int cpu, int imbalance_pct)
{
struct rq *rq = cpu_rq(cpu);
unsigned long total = weighted_cpuload(cpu);
@@ -3975,6 +3975,11 @@ static unsigned long target_load(int cpu)
if (!sched_feat(LB_BIAS))
return total;

+ /*
+ * Bias target load with imbalance_pct.
+ */
+ total = total * imbalance_pct / 100;
+
return max(rq->cpu_load, total);
}

@@ -4180,6 +4185,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
struct task_group *tg;
unsigned long weight;
int balanced;
+ int bias = 100 + (sd->imbalance_pct - 100) / 2;

/*
* If we wake multiple tasks be careful to not bounce
@@ -4191,7 +4197,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
this_cpu = smp_processor_id();
prev_cpu = task_cpu(p);
load = source_load(prev_cpu);
- this_load = target_load(this_cpu);
+ this_load = target_load(this_cpu, bias);

/*
* If sync wakeup then subtract the (maximum possible)
@@ -4226,7 +4232,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
this_eff_load *= this_load +
effective_load(tg, this_cpu, weight, weight);

- prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
+ prev_eff_load = bias;
prev_eff_load *= power_of(this_cpu);
prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

@@ -4247,7 +4253,8 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)

if (balanced ||
(this_load <= load &&
- this_load + target_load(prev_cpu) <= tl_per_task)) {
+ this_load + target_load(prev_cpu, sd->imbalance_pct)
+ <= tl_per_task)) {
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and
@@ -4293,7 +4300,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
if (local_group)
load = source_load(i);
else
- load = target_load(i);
+ load = target_load(i, imbalance);

avg_load += load;
}
@@ -4309,7 +4316,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
}
} while (group = group->next, group != sd->groups);

- if (!idlest || 100*this_load < imbalance*min_load)
+ if (!idlest || this_load < min_load)
return NULL;
return idlest;
}
@@ -5745,6 +5752,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
{
unsigned long load;
int i;
+ int bias = 100 + (env->sd->imbalance_pct - 100) / 2;

memset(sgs, 0, sizeof(*sgs));

@@ -5752,8 +5760,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
struct rq *rq = cpu_rq(i);

/* Bias balancing toward cpus of our domain */
- if (local_group)
- load = target_load(i);
+ if (local_group && env->idle != CPU_IDLE)
+ load = target_load(i, bias);
else
load = source_load(i);

@@ -6193,14 +6201,6 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
if ((local->idle_cpus < busiest->idle_cpus) &&
busiest->sum_nr_running <= busiest->group_weight)
goto out_balanced;
- } else {
- /*
- * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
- * imbalance_pct to be conservative.
- */
- if (100 * busiest->avg_load <=
- env->sd->imbalance_pct * local->avg_load)
- goto out_balanced;
}

force_balance:
--
1.8.1.2


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