linux-kernel - Re: Cryogenic: Enabling Power-Aware Applications on Linux

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Date:	Fri, 11 Apr 2014 17:10:18 -0700 (PDT)
From:	David Lang <david@...g.hm>
To:	Christian Grothoff <christian@...thoff.org>
cc:	Pavel Machek <pavel@....cz>,
	Alejandra Morales <alejandra.morales@....de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Cryogenic: Enabling Power-Aware Applications on Linux

On Sat, 12 Apr 2014, Christian Grothoff wrote:

> On 04/12/2014 12:05 AM, Pavel Machek wrote:
>> Hi!
>>
>>>>> Cryogenic is the result of my Master's Thesis, completed at the Technical University
>>>>> of Munich under the supervision of Christian Grothoff. You can find more information
>>>>> about Cryogenic at https://gnunet.org/cryogenic
>
>> Hmm, but the API needs redoing, anyway, fcntl()?
>
> Depends --- while I like the idea, I did not hear enough to be
> certain that having this feature embedded in such a non-modular
> way was already the consensus (and I do not see a reasonable
> way to change the API this way while maintaining the modularity
> of the current code).


hpa has a good track record for things like this, and there is very little 
desire in Linux for things to be kept as an optional add-on module (and cgroups 
is a very pointed example of what happens if a capability that people wants gets 
ignored).

this sort of capability is something that is very desirable, there are many 
people making attempts to provide this sort of event consolidation. So I think 
it's _very_ safe to say that if this is accepted, it will be a change to the 
core, not just a loadable module.

This means that you need to go through the work hpa was pointing you at, and you 
will also need to do some analysis of what the cost is to have this capability 
in place, but without the application making use of it (because anything 
remotely useful _will_ get enabled in a distro kernel, so how badly does it hurt 
high-performance server apps if it's compiled in)

David Lang
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