Re: [PATCH] sched/fair: use signed long when compute energy delta in eas

[Xuewen Yan]

Hi
> > >
> > > In fair.c:select_task_rq_fair(), if feec() returns a error (< 0), then
> > > prev_cpu is selected. I think it's better to still let feec() signal
> > > that something happened and let select_task_rq_fair() select prev_cpu by
> > > itself.
> > In fair.c:select_task_rq_fair(), when feec() returns a error (< 0),
> > the new_cpu = find_idlest_cpu() or select_idle_sibling().
> > In your patch, you should return prev_cpu instead of -1 if you want to
> > select the prev_cpu.
> Having a negative delta doesn't imply that prev_cpu is still available.
> E.g.: If prev_cpu cannot receive the task (and is skipped), and a
> negative delta appears when evaluating the other CPUs. In such case
> feec() cannot select prev_cpu. dst_cpu must be selected by another function.
In this case, would it be better to add a condition "prev_delta == ULONG_MAX" ?
Returnig(-1)  could avoid the negative delta, but I still think this
is not the fundamental way to solve the problem.
But I think you can send a V2 with the bail out mechanism.

Regards