Xen is a feature
From: Jeremy Fitzhardinge
Date: Thu May 28 2009 - 20:45:56 EST
Ingo Molnar wrote:
Xen changes - especially dom0 - are overwhelmingly not about
improving Linux, but about having some special hook and extra
treatment in random places - and that's really bad.
You've made this argument a few times now, and I take exception to it.
It seems to be predicated on the idea that Xen has some kind of niche
usage, with barely more users than Voyager. Or that it is a parasite
sitting on the side of Linux, being a pure drain.
Neither is true. Xen is very widely used. There are at least 500k
servers running Xen in commercial user sites (and untold numbers of
smaller sites and personal users), running millions of virtual guest
domains. If you browse the net at all widely, you're likely to be using
a Xen-based server; all of Amazon runs on Xen, for example. Mozilla and
Debian are hosted on Xen systems.
Hardware vendors like Dell and HP are shipping servers with Xen built
into the firmware, and increasingly, desktops and laptops. Many laptop
"instant-on/instant-access" features are based on a combination of Xen
All major Linux distributions support running as a Xen guest, and many
support running as a Xen host.
For these users, Xen support is an active feature of Linux; Linux
without Xen support would be much less useful to them, and better Xen
support would be more useful. For them, Xen support is no different
from any other kind of platform support. They are being actively
hampered by the fact that the only dom0 support is available in the form
of either ancient or very patched kernels.
To them, improved Xen support *is* "improving Linux".
Your view appears to be that virtualization is either useless, or a neat
trick useful for doing a quick kernel test (which is why kvm got early
traction in this community; it is well suited to this use-case). But
that is a very parochial kernel-dev view. For many users,
virtualization (in general, but commonly on Xen) has become an
absolutely essential part of their computing infrastructure, and they
would no more go without it than they would go without ethernet.
We're taking your technical critiques very seriously, of course, and I
appreciate any constructive comment. But your baseline position of
animosity towards Xen is unreasonable, unfair and unnecessary.
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