Commit 88b8dac0 makes load_balance() consider other cpus in its group.
But, in that, there is no code for preventing to re-select dst-cpu.
So, same dst-cpu can be selected over and over.
This patch add functionality to load_balance() in order to exclude
cpu which is selected once.
Cc: Srivatsa Vaddagiri <va...@linux.vnet.ibm.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e6f8783..d4c6ed0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6814,6 +6814,7 @@ struct task_group root_task_group;
LIST_HEAD(task_groups);
#endif
+DECLARE_PER_CPU(cpumask_var_t, load_balance_dst_grp);
DECLARE_PER_CPU(cpumask_var_t, load_balance_cpu_active);
void __init sched_init(void)
@@ -6828,7 +6829,7 @@ void __init sched_init(void)
alloc_size += 2 * nr_cpu_ids * sizeof(void **);
#endif
#ifdef CONFIG_CPUMASK_OFFSTACK
- alloc_size += num_possible_cpus() * cpumask_size();
+ alloc_size += num_possible_cpus() * cpumask_size() * 2;
#endif
if (alloc_size) {
ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
@@ -6851,6 +6852,8 @@ void __init sched_init(void)
#endif /* CONFIG_RT_GROUP_SCHED */
#ifdef CONFIG_CPUMASK_OFFSTACK
for_each_possible_cpu(i) {
+ per_cpu(load_balance_dst_grp, i) = (void *)ptr;
+ ptr += cpumask_size();
per_cpu(load_balance_cpu_active, i) = (void *)ptr;
ptr += cpumask_size();
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7382fa5..70631e8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4974,6 +4974,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
#define MAX_PINNED_INTERVAL 512
/* Working cpumask for load_balance and load_balance_newidle. */
+DEFINE_PER_CPU(cpumask_var_t, load_balance_dst_grp);
DEFINE_PER_CPU(cpumask_var_t, load_balance_cpu_active);
static int need_active_balance(struct lb_env *env)
@@ -5005,17 +5006,17 @@ static int load_balance(int this_cpu, struct rq
*this_rq,
int *balance)
{
int ld_moved, cur_ld_moved, active_balance = 0;
- int lb_iterations, max_lb_iterations;
struct sched_group *group;
struct rq *busiest;
unsigned long flags;
+ struct cpumask *dst_grp = __get_cpu_var(load_balance_dst_grp);
struct cpumask *cpus = __get_cpu_var(load_balance_cpu_active);
struct lb_env env = {
.sd = sd,
.dst_cpu = this_cpu,
.dst_rq = this_rq,
- .dst_grpmask = sched_group_cpus(sd->groups),
+ .dst_grpmask = dst_grp,
.idle = idle,
.loop_break = sched_nr_migrate_break,
.cpus = cpus,
@@ -5025,9 +5026,9 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* other cpus in our group */
if (idle == CPU_NEWLY_IDLE) {
env.dst_grpmask = NULL;
- max_lb_iterations = 0;
} else {
- max_lb_iterations = cpumask_weight(env.dst_grpmask);
+ cpumask_copy(dst_grp, sched_group_cpus(sd->groups));
+ cpumask_clear_cpu(env.dst_cpu, env.dst_grpmask);
}
cpumask_copy(cpus, cpu_active_mask);
@@ -5055,7 +5056,6 @@ redo:
schedstat_add(sd, lb_imbalance[idle], env.imbalance);
ld_moved = 0;
- lb_iterations = 1;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
@@ -5112,14 +5112,17 @@ more_balance:
* moreover subsequent load balance cycles should correct the
* excess load moved.
*/
- if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
- lb_iterations++ < max_lb_iterations) {
+ if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
env.dst_rq = cpu_rq(env.new_dst_cpu);
env.dst_cpu = env.new_dst_cpu;
env.flags &= ~LBF_SOME_PINNED;
env.loop = 0;
env.loop_break = sched_nr_migrate_break;
+
+ /* Prevent to re-select dst_cpu */
+ cpumask_clear_cpu(env.dst_cpu, env.dst_grpmask);
+
/*
* Go back to "more_balance" rather than "redo" since we
* need to continue with same src_cpu.
--
1.7.9.5
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