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. We prevent to re-select dst_cpu via
env's cpus, so now, env's cpus is a candidate not only for src_cpus,
but also dst_cpus.
Cc: Srivatsa Vaddagiri <va...@linux.vnet.ibm.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e3f09f4..6f238d2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3883,7 +3883,7 @@ int can_migrate_task(struct task_struct *p, struct lb_env
*env)
return 0;
if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
- int new_dst_cpu;
+ int cpu;
schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
@@ -3898,12 +3898,14 @@ int can_migrate_task(struct task_struct *p, struct
lb_env *env)
if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
return 0;
- new_dst_cpu = cpumask_first_and(env->dst_grpmask,
- tsk_cpus_allowed(p));
- if (new_dst_cpu < nr_cpu_ids) {
- env->flags |= LBF_SOME_PINNED;
- env->new_dst_cpu = new_dst_cpu;
- }
+ /* Prevent to re-select dst_cpu via env's cpus */
+ for_each_cpu_and(cpu, env->dst_grpmask, env->cpus)
+ if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
+ env->flags |= LBF_SOME_PINNED;
+ env->new_dst_cpu = cpu;
+ break;
+ }
+
return 0;
}
@@ -4989,7 +4991,6 @@ 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;
@@ -5009,11 +5010,6 @@ 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;
- /* we don't care max_lb_iterations in this case,
- * in following patch, this will be removed */
- max_lb_iterations = 0;
- } else {
- max_lb_iterations = cpumask_weight(env.dst_grpmask);
}
cpumask_copy(cpus, cpu_active_mask);
@@ -5041,7 +5037,6 @@ 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
@@ -5098,14 +5093,17 @@ 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 via env's cpus */
+ cpumask_clear_cpu(env.dst_cpu, env.cpus);
+
/*
* 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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