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

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Date:	Thu, 21 Feb 2013 09:43:11 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
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

On 02/20/2013 11:41 PM, Ingo Molnar wrote:
> 
> * Alex Shi <alex.shi@...el.com> wrote:
> 
>> Now there is just 2 types policy: performance and 
>> powersaving(with 2 degrees, powersaving and balance).
> 
> I don't think we really want to have 'degrees' to the policies 
> at this point - we want each policy to be extremely good at what 
> it aims to do:
> 
>  - 'performance' should finish jobs in in the least amount of 
>     time possible. No ifs and whens.
> 
>  - 'power saving' should finish jobs with the least amount of 
>     watts consumed. No ifs and whens.
> 
>> powersaving policy will try to assign one task to each LCPU, 
>> whichever the LCPU is SMT thread or a core. The balance policy 
>> is also a kind of powersaving policy, just a bit less 
>> aggressive. It will try to assign tasks according group 
>> capacity, one task to one capacity.
> 
> The thing is, 'a bit less aggressive' is an awfully vague 
> concept to maintain on a long term basis - while the two 
> definitions above are reasonably deterministic which can be 
> measured and improved upon.
> 
> Those two policies and definitions are also much easier to 
> communicate to user-space and to users - it's much easier to 
> explain what each policy is supposed to do.
> 
> I'd be totally glad if we got so far that those two policies 
> work really well. Any further nuance visible at the ABI level is 
> I think many years down the road - if at all. Simple things 
> first - those are complex enough already.


Thanks for comments!
I will remove the 'balance' policy.

> 
> Thanks,
> 
> 	Ingo
> 


-- 
Thanks Alex
--
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