On 19/05/17 14:31, Dietmar Eggemann wrote:
> On 18/05/17 20:36, Jeffrey Hugo wrote:
>
> [...]
>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index d711093..a5d41b1 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -8220,7 +8220,24 @@ static int load_balance(int this_cpu, struct rq
>> *this_rq,
>> /* All tasks on this runqueue were pinned by CPU affinity */
>> if (unlikely(env.flags & LBF_ALL_PINNED)) {
>> cpumask_clear_cpu(cpu_of(busiest), cpus);
>> - if (!cpumask_empty(cpus)) {
>> + /*
>> + * dst_cpu is not a valid busiest cpu in the following
>> + * check since load cannot be pulled from dst_cpu to be
>> + * put on dst_cpu.
>> + */
>> + cpumask_clear_cpu(env.dst_cpu, cpus);
>> + /*
>> + * Go back to "redo" iff the load-balance cpumask
>> + * contains other potential busiest cpus for the
>> + * current sched domain.
>> + */
>> + if (cpumask_intersects(cpus,
>> sched_domain_span(env.sd))) {
>> + /*
>> + * Now that the check has passed, reenable
>> + * dst_cpu so that load can be calculated on
>> + * it in the redo path.
>> + */
>> + cpumask_set_cpu(env.dst_cpu, cpus);
>
> IMHO, this will work nicely and its way easier.
This was too quick ... if we still have other potential dst cpus
available and cpu_of(busiest) is the latest src cpu then this will fail.
It does work on sd with 'group_weight == 1', e.g. your MC sd 'sd->child
== NULL'.
But IMHO 'group_imbalance' propagation has to work on higher sd levels
as well.
> Another idea might be to check if the LBF_ALL_PINNED is set when we
> check if we should clean the imbalance flag.
>
> @@ -8307,14 +8307,13 @@ static int load_balance(int this_cpu, struct rq
> *this_rq,
> * We reach balance although we may have faced some affinity
> * constraints. Clear the imbalance flag if it was set.
> */
> - if (sd_parent) {
> + if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
> int *group_imbalance = &sd_parent->groups->sgc->imbalance;
>
> if (*group_imbalance)
> *group_imbalance = 0;
> }
[...]
