Re: false nr_running check in load balance?

[Paul Turner]

On Tue, Aug 13, 2013 at 12:38 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Tue, Aug 13, 2013 at 12:45:12PM +0800, Lei Wen wrote:
>> > Not quite right; I think you need busiest->cfs.h_nr_running.
>> > cfs.nr_running is the number of entries running in this 'group'. If
>> > you've got nested groups like:
>> >
>> >  'root'
>> >    \
>> >    'A'
>> >    / \
>> >   t1 t2
>> >
>> > root.nr_running := 1 'A', even though you've got multiple running tasks.
>> >
>>
>> You're absolutely right for this. :)
>> I miss it for not considering the group case...
>>
>> Then do you think it is necessary to do below change in load_balance() code?
>>  -       if (busiest->nr_running > 1) {
>>  +       if (busiest->cfs.h_nr_running > 1) {
>>
>
> Yes I think that would be fine.

If we pivot to use h_nr_running we should probably also update
call-sites such as cpu_load_avg_per_task() for consistency.
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