[uml-devel] Xen going to be in Kernel 2.6 soon?

[uml-devel] Xen going to be in Kernel 2.6 soon?

[Sven Köhler]

Hi,

according to the german news-magazine heise.de, Xen will be in Kernel 
2.6 soon. I feel like this is a slap in Jeff's face, since i thought 
that UML will be developed as the first choice in virtualizations 
techniques. I also thought, that UML will perhaps soon be as fast as Xen 
since SKAS4 is on horizon.

So what is it all about? When should somebody chose Xen, and when should 
somebody chose UML? and how will UML and Xen compete?

Thx
   Sven



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Sky, comma, falling. (Was Re: [uml-devel] Xen going to be in Kernel 2.6 soon?)

[Rob Landley]

On Friday 04 February 2005 08:45 pm, Sven Köhler wrote:
>  I feel like this is a slap in Jeff's face, since i thought 
> that UML will be developed as the first choice in virtualizations 
> techniques.

Yup, just like the inclusion of reiserfs in the kernel is a slap in the face 
to ext3.  Obviously they did it just to be insulting, didn't you read Linus's 
"I'm a bastard" speech?

> So what is it all about? When should somebody chose Xen, and when should
> somebody chose UML? and how will UML and Xen compete?

You know, ever since the release of the BSD source code in 1992 totally 
derailed that "Linux" project people were playing with back then, this kind 
of question has become vitally important.  The release of any remotely 
similar project obviously can immediately halt all development of established 
projects that developers have sunk years of effort into, and they immediately 
start porting over things like the COW mounts and hostfs and honeypot procfs, 
and rewrite all the existing tutorials and retrain everybody overnight to 
work on the new as yet untested thingy that hasn't been particularly debugged 
yet.

Especially in a case like this, where Xen actually competes with VMWare rather 
than UML.  Obviously, UML is doomed.  What with Xen requiring a modified host 
kernel to provide its virtualization environment whereas UML uses the process 
abstraction to virtualize it: I mean, who's going to use _processes_ in five 
years, will future kernels even bother to support them?  Sure, UML not only 
runs on an unmodified Linux kernel (even running a 2.6 UML on a 2.2 host 
kernel), and even an effort underway to get it running on windows (who knows 
why, but a MacOS X host can only be a matter of time), but that just means 
maybe it can scrape on some tiny niches once it's driven off Linux by this 
new "Adeos" thing...  Er, I mean "Plex86"...  Um...  "Xen", that's it.  And 
obviously its original use as a Linux development tool letting you do things 
like create a filesystem driver and mount an instance of it without 
destablizing your host kernel, or run bits of the kernel under normal 
userspace debugging tools...  Well, we're well rid of that, aren't we?  And 
being to swap kernel memory to backing store just like a regular application, 
that was obviously a bad idea from day one...

Why was the question interesting again?

Rob


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Re: Sky, comma, falling. (Was Re: [uml-devel] Xen going to be in Kernel 2.6 soon?)

[Sven Köhler]

>> I feel like this is a slap in Jeff's face, since i thought 
>>that UML will be developed as the first choice in virtualizations 
>>techniques.
> 
> Yup, just like the inclusion of reiserfs in the kernel is a slap in the face 
> to ext3.  Obviously they did it just to be insulting, didn't you read Linus's 
> "I'm a bastard" speech?

No, i don't know that speech. In addition i like reiserfs, so i'm 
perhaps the wrong person to discuss that with. The next thing on the 
horizon is reiser4 - perhaps with the "files as directory" feature - 
what ever that means, but i guess i won't like it.

>>So what is it all about? When should somebody chose Xen, and when should
>>somebody chose UML? and how will UML and Xen compete?
> 
> You know, ever since the release of the BSD source code in 1992 totally 
> derailed that "Linux" project people were playing with back then, this kind 
> of question has become vitally important.  The release of any remotely 
> similar project obviously can immediately halt all development of established 
> projects that developers have sunk years of effort into, and they immediately 
> start porting over things like the COW mounts and hostfs and honeypot procfs, 
> and rewrite all the existing tutorials and retrain everybody overnight to 
> work on the new as yet untested thingy that hasn't been particularly debugged 
> yet.

So you critisize, that they don't concentrate forces on UML? I Agree.

With the integration of UML into the Linux-Kernel i thought, that it 
would speed up development of UML and make it more stable. Intead, the 
people still break the UML-stuff regularly and Jeff and Blaisorblade 
must provide patches again :-(

> Especially in a case like this, where Xen actually competes with VMWare rather 
> than UML.  Obviously, UML is doomed.  What with Xen requiring a modified host 
> kernel to provide its virtualization environment whereas UML uses the process 
> abstraction to virtualize it: I mean, who's going to use _processes_ in five 
> years, will future kernels even bother to support them?  Sure, UML not only 
> runs on an unmodified Linux kernel (even running a 2.6 UML on a 2.2 host 
> kernel), and even an effort underway to get it running on windows (who knows 
> why, but a MacOS X host can only be a matter of time), but that just means 
> maybe it can scrape on some tiny niches once it's driven off Linux by this 
> new "Adeos" thing...  Er, I mean "Plex86"...  Um...  "Xen", that's it.  And 
> obviously its original use as a Linux development tool letting you do things 
> like create a filesystem driver and mount an instance of it without 
> destablizing your host kernel, or run bits of the kernel under normal 
> userspace debugging tools...  Well, we're well rid of that, aren't we?  And 
> being to swap kernel memory to backing store just like a regular application, 
> that was obviously a bad idea from day one...

VMWare, Xen and UML are different techniques. As far as i know, UML 
doesn't use processes as the virtualization environment when running in 
SKAS mode. It runs a new kernel within a different address space - 
afaik, this is more like VMWare and Xen. But due to haveing a relatively 
normal hostsystem, there are the advantages you mentioned.

You also forgot some things: Xen doesn't support NPTL too

> Why was the question interesting again?

What's the future of Xen and UML? Will Xen grow bigger than UML? Which 
is Linus's favourite? UML or Xen?


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Re: Sky, comma, falling. (Was Re: [uml-devel] Xen going to be in Kernel 2.6 soon?)

[Rob Landley]

On Saturday 05 February 2005 09:46 am, Sven Köhler wrote:
> > read Linus's "I'm a bastard" speech?
>
> No, i don't know that speech.

You obviously didn't google for "linus bastard speech", either.  It's the 
first hit.

>> You know, ever since the release of the BSD source code in 1992 totally 
>> derailed that "Linux" project people were playing with back then, this kind 
>> of question has become vitally important.
...
> So you critisize, that they don't concentrate forces on UML? I Agree.

American non sequitur society: we don't make sense, but we do like pizza.

Okay, hint: if BSD had "totally derailed" Linux back in 1992, why would we now 
be talking about how to virtualize Linux?  Anyone?  Anyone?  (Would <sarcasm> 
</sarcasm> tags around the whole thing have helped?)

> > Why was the question interesting again?
>
> What's the future of Xen and UML? Will Xen grow bigger than UML? Which
> is Linus's favourite? UML or Xen?

Wow.  It _was_ possible to miss the sarcasm content of the first post.  And 
here I thought that it wasn't merely dripping with it, but that the sucker 
had been thorougly hosed down to the point of immersion, and had extra nailed 
to the side.

To answer the explicit questions for the sarcasm-blind: 1) UML development 
continues, Xen is a different project that competes with VMWare over in a 
different niche.  2) Who cares?  3) Linus doesn't use either one, so it would 
be tough for him to play favorites even if he was in the habit of playing 
favorites, which he's not.  4) You missed Adeos and Plex86.

I'm going to put away the troll food now.

Rob


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Re: [uml-devel] Xen going to be in Kernel 2.6 soon?

[Jeff Dike]

skoehler@upb.de said:
> according to the german news-magazine heise.de, Xen will be in Kernel
> 2.6 soon. 

What Linus is quoted as saying is that it will go into 2.6.  This is consistent
with Xen going into 2.6.47 or something.  I don't get the feeling that it
will go in soon because aspects of the design are fairly controversial.

> I feel like this is a slap in Jeff's face, since i thought
> that UML will be developed as the first choice in virtualizations
> techniques. 

UML has never has any sort of privileged status.  Never has, never will.
Everything has to compete on its merits.  

> I also thought, that UML will perhaps soon be as fast as
> Xen  since SKAS4 is on horizon.

skas4 is an interface change, not a speedup.  As far as speed goes, I have
a bunch of nice things in my current patchset, like skas0, system call and
tlb flushing optimizations.  Also, we (me and some other Intel people) are
working on having UML support Intel's VT virtualization extensions, which
will bring it much closer to hardware speed.

So, as Rob Landley pointed out, except with much more sarcasm, the sky is
not falling.

				Jeff



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Re: Sky, comma, falling. (Was Re: [uml-devel] Xen going to be in Kernel 2.6 soon?)

[Geert Uytterhoeven]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 753 bytes --]

On Sat, 5 Feb 2005, Sven Köhler wrote:
> With the integration of UML into the Linux-Kernel i thought, that it would
> speed up development of UML and make it more stable. Intead, the people still
> break the UML-stuff regularly and Jeff and Blaisorblade must provide patches
> again :-(

That's true for _all_ architectures these days[*], not even for UML.

Gr{oetje,eeting}s,

						Geert

[*] i386 lost its privilege of never being broken since Linus got a G5 ;-)
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: Sky, comma, falling. (Was Re: [uml-devel] Xen going to be in Kernel 2.6 soon?)

[Rob Landley]

On Monday 07 February 2005 04:56 am, Geert Uytterhoeven wrote:
> On Sat, 5 Feb 2005, Sven Köhler wrote:
> > With the integration of UML into the Linux-Kernel i thought, that it
> > would speed up development of UML and make it more stable. Intead, the
> > people still break the UML-stuff regularly and Jeff and Blaisorblade must
> > provide patches again :-(
>
> That's true for _all_ architectures these days[*], not even for UML.

It's the 2.6 development model.  We haven't got a stable series anymore, now 
_everybody_ tests the odd releases. :)

> Gr{oetje,eeting}s,
>
> 						Geert
>
> [*] i386 lost its privilege of never being broken since Linus got a G5 ;-)

If the Apple Store ever calls me back about that darn mac mini waiting list, 
porting UML to MacOS X may stop being theoretical.  (After I get done playing 
World of Warcraft, anyway...)

Rob


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