Re: [patch v5 04/15] sched: add sched balance policies in kernel

Ingo Molnar
2013-02-20T09:37:58Z

* Alex Shi <alex.shi@intel.com> wrote:

> Current scheduler behavior is just consider for larger
> performance of system. So it try to spread tasks on more cpu
> sockets and cpu cores
>
> To adding the consideration of power awareness, the patchset
> adds 2 kinds of scheduler policy: powersaving and balance.
> They will use runnable load util in scheduler balancing. The
> current scheduling is taken as performance policy.
>
> performance: the current scheduling behaviour, try to spread tasks
> on more CPU sockets or cores. performance oriented.
> powersaving: will pack tasks into few sched group until all LCPU in the
> group is full, power oriented.
> balance : will pack tasks into few sched group until group_capacity
> numbers CPU is full, balance between performance and
> powersaving.

Hm, so in a previous review I suggested keeping two main
policies: power-saving and performance, plus a third, default
policy, which automatically switches between these two if/when
the kernel has information about whether a system is on battery
or on AC - and picking 'performance' when it has no information.

Such an automatic policy would obviously be useful to users -
and that is what makes such a feature really interesting and a
step forward.

I think Peter expressed similar views: we don't want many knobs
and states, we want two major goals plus an (optional but
default enabled) automatism.

Is your 'balance' policy implementing that suggestion?
If not, why not?

Thanks,

Ingo