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

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Message-ID: <20130220093751.GA2444@gmail.com>
Date:	Wed, 20 Feb 2013 10:37:51 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	torvalds@...ux-foundation.org, mingo@...hat.com,
	peterz@...radead.org, 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, morten.rasmussen@....com
Subject: Re: [patch v5 04/15] sched: add sched balance policies in kernel


* Alex Shi <alex.shi@...el.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
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