Date: Wed, 6 Apr 2011 12:55:47 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Olivier Galibert <galibert@pobox.com>
Cc: Avi Kivity <avi@redhat.com>, Anthony Liguori <anthony@codemonkey.ws>,
        Pekka Enberg <penberg@kernel.org>, linux-kernel@vger.kernel.org,
        aarcange@redhat.com, mtosatti@redhat.com, kvm@vger.kernel.org,
        joro@8bytes.org, penberg@cs.helsinki.fi, asias.hejun@gmail.com,
        gorcunov@gmail.com
Subject: Re: [ANNOUNCE] Native Linux KVM tool
Message-ID: <20110406105547.GA13766@elte.hu>
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* Olivier Galibert <galibert@pobox.com> wrote:

> On Wed, Apr 06, 2011 at 11:33:33AM +0200, Ingo Molnar wrote:
> > Examples: X11 and GCC - both were struggling for years to break through magic 
> > invisible barriers of growth and IMHO a lot of it had to do with the lack of 
> > code (and development model) cleanliness.
> 
> A large part of what's killing X11 and qemu is the decomposition in
> multiple trees and the requirement that every version must work with
> every other version.
> 
> For X11 you have:
> - the server
> - the protocol headers
> - the individual 2D drivers
> - libdrm
> - the kernel
> - mesa
> - the video decoding driver/libs
> 
> For qemu you have:
> - qemu
> - qemu-kvm
> - the kernel
> - libvirt
> - seabios
> 
> Any reaching change ends up hitting most of the trees, with all to
> coordination that means.  And in any case you're supposed to handle
> any version of the other components.

Splitting up a project into several trees, often unnecessarily, is a 
self-inflicted wound really.

Smaller projects can hurt from that as well: a well-known example is oprofile.

Pointing to the stupidity of overmodularization is one of my pet peeves, i 
consider it a "development model cleanliness" bug that needlessly exposes OSS 
projects to the negative effects of technical and social forks and 
complicates/shackles them. I flamed^W argued about it before, in the KVM / Qemu 
context as well.

There are good examples of successful, highly integrated projects:

  - FreeBSD - it has achieved Linux-alike results with a fraction of the
              manpower

  - Android - on the desktop it has achieved much more than Linux, with a
              fraction of the manpower

And that concept can be brought to its logical conclusion: i think it's only a 
matter of time until someone takes the Linux kernel, integrates klibc and a 
toolchain into it with some good initial userspace and goes wild with that 
concept, as a single, sane, 100% self-hosting and self-sufficient OSS project, 
tracking the release schedule of the Linux kernel.

It might not happen on PC hardware (which is *way* too OSS-hostile), but it 
will eventually happen IMO. It's the eventual OSS killer feature and weirdly 
enough no-one has tried it yet. (Android comes close in a sense)

Thanks,

	Ingo
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