Re: Scheduling the highest priority task

[Ingo Molnar]

* Martin Roehricht <ml@xxxxxxxxxxx> wrote:

> On 08/02/2007 01:40 PM, Ingo Molnar wrote:
> >in the SMP migration code, the 'old scheduler' indeed picks the lowest 
> >priority one, _except_ if that task is running on another CPU or is too 
> >'cache hot':
> 
> But why is it, that the scheduler picks the lowest priority one? I 
> thought sched_find_first_bit() picks the index of the lowest order bit 
> in the bitmap and thus the highest priority job. Is that wrong? What 
> needs to be changed to let the scheduler pick the highest priority 
> task from a given runqueue? I am very confused ...

it first picks the lowest index (i.e. the highest priority active 
priority-queue), but within those tasks (each task in that priority 
queue has equal priority) the load-balancer has freedom to pick any. 
Based on performance data we went for picking from the tail of the 
queue.

	Ingo
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