linux-kernel - Re: [RFC] Unify KVM kernel-space and user-space code into a single project

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Message-ID: <4BA20EB8.60707@redhat.com>
Date:	Thu, 18 Mar 2010 13:30:00 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Anthony Liguori <anthony@...emonkey.ws>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sheng Yang <sheng@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	oerg Roedel <joro@...tes.org>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, ziteng.huang@...el.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Fr?d?ric Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single
 project

On 03/18/2010 12:50 PM, Ingo Molnar wrote:
> * Avi Kivity<avi@...hat.com>  wrote:
>
>    
>>> The moment any change (be it as trivial as fixing a GUI detail or as
>>> complex as a new feature) involves two or more packages, development speed
>>> slows down to a crawl - while the complexity of the change might be very
>>> low!
>>>        
>> Why is that?
>>      
> It's very simple: because the contribution latencies and overhead compound,
> almost inevitably.
>    

It's not inevitable, if the projects are badly run, you'll have high 
latencies, but projects don't have to be badly run.

> If you ever tried to implement a combo GCC+glibc+kernel feature you'll know
> ...
>
> Even with the best-run projects in existence it takes forever and is very
> painful - and here i talk about first hand experience over many years.
>    

Try sending a patch to qemu-devel@, you may be pleasantly surprised.


>> I the maintainers of all packages are cooperative and responsive, then the
>> patches will get accepted quickly.  If they aren't, development will be
>> slow. [...]
>>      
> I'm afraid practice is different from the rosy ideal you paint there. Even
> with assumed 'perfect projects' there's always random differences between
> projects, causing doubled (tripled) overhead and compounded up overhead:
>
>   - random differences in release schedules
>
>   - random differences in contribution guidelines
>
>   - random differences in coding style
>    

None of these matter for steady contributors.

>> [...] It isn't any different from contributing to two unrelated kernel
>> subsystems (which are in fact in different repositories until the next merge
>> window).
>>      
> You mention a perfect example: contributing to multipe kernel subsystems. Even
> _that_ is very noticeably harder than contributing to a single subsystem - due
> to the inevitable buerocratic overhead, due to different development trees,
> due to different merge criteria.
>
> So you are underlining my point (perhaps without intending to): treating
> closely related bits of technology as a single project is much better.
>
> Obviously arch/x86/kvm/, virt/ and tools/kvm/ should live in a single
> development repository (perhaps micro-differentiated by a few topical
> branches), for exactly those reasons you mention.
>    

How is a patch for the qemu GUI eject button and the kvm shadow mmu 
related?  Should a single maintainer deal with both?


-- 
error compiling committee.c: too many arguments to function

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