On 4 November 2014 11:42, Wanpeng Li <kernel...@gmail.com> wrote:
> Hi Vincent,
>
>>>> +
>>>> +/*
>>>> * Group imbalance indicates (and tries to solve) the problem where
>>>> balancing
>>>> * groups is inadequate due to tsk_cpus_allowed() constraints.
>>>> *
>>>> @@ -6562,6 +6574,28 @@ static int need_active_balance(struct lb_env
>>>> *env)
>>>> return 1;
>>>> }
>>>> + /*
>>>> + * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
>>>
>>>
>>> Why specify one task instead of not less than one?
>>
>> if cfs.h_nr_running == 0 (which should not occurs at that point), we
>> don't need to do more test to check if it's worth moving the task
>> because there is no task to move.
>
>
> Sorry for my confusing statement. I mean cfs.h_nr_running >= 1.
ok.
If we have more than 1 task, we fall back into the default balancing
policy than should move a not running task or that will use the
imbalance field in case of the presence of pinned tasks
Regards,
Vincent
>
> Regards,
> Wanpeng Li
>
>
>>
>> Regards,
>> Vincent
>>>
>>> Regards,
>>> Wanpeng Li
>>>
>>>
>>>> + * It's worth migrating the task if the src_cpu's capacity is
>>>> reduced
>>>> + * because of other sched_class or IRQs whereas capacity stays
>>>> + * available on dst_cpu.
>>>> + */
>>>> + if ((env->idle != CPU_NOT_IDLE) &&
>>>> + (env->src_rq->cfs.h_nr_running == 1)) {
>>>> + unsigned long src_eff_capacity, dst_eff_capacity;
>>>> +
>>>> + dst_eff_capacity = 100;
>>>> + dst_eff_capacity *= capacity_of(env->dst_cpu);
>>>> + dst_eff_capacity *= capacity_orig_of(env->src_cpu);
>>>> +
>>>> + src_eff_capacity = sd->imbalance_pct;
>>>> + src_eff_capacity *= capacity_of(env->src_cpu);
>>>> + src_eff_capacity *= capacity_orig_of(env->dst_cpu);
>>>> +
>>>> + if (src_eff_capacity < dst_eff_capacity)
>>>> + return 1;
>>>> + }
>>>> +
--
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