linux-kernel - Re: [patch v4 09/18] sched: add sched

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Date:	Tue, 12 Feb 2013 11:36:01 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	torvalds@...ux-foundation.org, mingo@...hat.com,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	arjan@...ux.intel.com, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 09/18] sched: add sched_policies in kernel

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_PERFORMANCE	(0x1)
> +#define SCHED_POLICY_POWERSAVING	(0x2)
> +#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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