Re: [patch v4 03/18] sched: fix find_idlest_group mess logical

[Alex Shi]

On 02/12/2013 06:16 PM, Peter Zijlstra wrote:
> On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote:
>> There is 4 situations in the function:
>> 1, no task allowed group;
>> 	so min_load = ULONG_MAX, this_load = 0, idlest = NULL
>> 2, only local group task allowed;
>> 	so min_load = ULONG_MAX, this_load assigned, idlest = NULL
>> 3, only non-local task group allowed;
>> 	so min_load assigned, this_load = 0, idlest != NULL
>> 4, local group + another group are task allowed.
>> 	so min_load assigned, this_load assigned, idlest != NULL
>>
>> Current logical will return NULL in first 3 kinds of scenarios.
>> And still return NULL, if idlest group is heavier then the
>> local group in the 4th situation.
>>
>> Actually, I thought groups in situation 2,3 are also eligible to host
>> the task. And in 4th situation, agree to bias toward local group.
> 
> I'm not convinced this is actually a cleanup.. taken together with patch
> 4 (which is a direct consequence of this patch afaict) you replace one
> conditional with 2.
> 

The current logical will always miss the eligible CPU in the 3rd
situation.  'sd = sd->child' still skip the non-local group eligible CPU.


-- 
Thanks
    Alex
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