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

From: Peter Zijlstra
Date: Tue Feb 12 2013 - 05:16:55 EST


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.

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