Re: [patch v4 09/18] sched: add sched_policies in kernel

From: Peter Zijlstra
Date: Tue Feb 12 2013 - 05:36:10 EST

On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote:
> Current scheduler behavior is just consider the 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.

_WHY_ do you start out with so much choice?

If your power policy is so abysmally poor on performance that you
already know you need a 3rd policy to keep people happy, maybe you're
doing something wrong?

> +#define SCHED_POLICY_BALANCE (0x4)
> +
> +extern int __read_mostly sched_policy;

I'd much prefer: sched_balance_policy. Scheduler policy is a concept
already well defined by posix and we don't need it to mean two
completely different things.

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