RE: [Xen-devel] RE: [Xen-users] (Xenlinux) gentoo-xen-kernel patches questions?

[Mike Viau <viaum@xxxxxxxxxxxxxxx>]

Mon, 5 Apr 2010 11:17:09 -0700 <jeremy@xxxxxxxx> wrote:
>
> On 04/02/2010 11:03 AM, Mike Viau wrote:
> > >>Hi,
> > >>
> > >>I noticed that the Xenlinux 2.6.33 patches are tagged as being
> > "Deprecated" but the 2.6.31 are not.
> > >>
> > >>May I ask why?
> > >>
> > >>http://code.google.com/p/gentoo-xen-kernel/downloads/list?can=1&q=&colspec=Filename+Summary+Uploaded+Size+DownloadCount
> > >>
> > >>
> > > Fri, 2 Apr 2010 13:15:09 -0400 <konrad.wilk@xxxxxxxxxx> wrote:
> > >
> > > No idea. But those patches are pursuing an entirely different method of
> > > getting Linux to work in privileged state (Dom0). The current
> > > development is with the pv-ops one:
> > >
> > > http://wiki.xensource.com/xenwiki/XenParavirtOps
> > >
> >
> > I am currently using the unstable version of debain's pvops xen kernel.
> >
> > http://packages.debian.org/sid/linux-image-2.6.32-4-xen-amd64
> >
> > It appears to have functioning networking and block devices which is
> > nice, but I have experienced some instabilities such as kernel dumping
> > on reboots. Unfortunately I do not have a console setup to log kernel
> > messages for this machine.
>
> That would be interesting to see. I have also seen oops messages on
> reboot, if you reboot while domains are still running. For me, at
> least, it appears to be a bug in blktap2. It would be useful if you
> could confirm that's what your crashes are, or if its something else.

Just paid for another term at school, so when I get some more cash I plan to go pickup an add-in serial card for my server and setup kernel logging to capture the messages on my laptop.

>
> > Would compiling the pv_ops kernel from the git repository produce any
> > additional stability?
>
> I'm not really sure what the Debian image is built from, so its hard to
> say. I'm getting the impression that their build is pretty closely
> tracking xen.git now. Are you seeing any other stability problems?

Firstly I am still in the process of testing but....

I don't have figures (benchmark results) on this however on my setup I noticed a decreasing disk IO responsiveness as uptime increased. The disk access returned to near native performance after a reboot though. 

On that note about rebooting, the machine seemed to reboot fine when only the Domian 0 was left running. Since I have not tested any DomUs without networking it is possible that is due to a bug in blktap2.


> Because, honestly, a crash while rebooting is annoying and should be
> fixed, it doesn't really count as a stability problem if you're
> rebooting anyway ;). (Unless it either prevents the reboot from
> working, or causes data-corruption on disk.)
>

Agreed, though I would tend to be more worried if I didn't have physical access to the box, which in this home scaled project I thankfully do.

Lastly, I must thank you Jeremy for all your hard work and contribution made to the Xen community :)


> > It was my understanding that one could run a stable Xen systems today
> > with a Xenlinux kernel, as pv_ops was still in development. I've read
> > on the XenParavirtsOps page that there are features available to Xen
> > but are not yet available in the pv_ops kernel (perhaps this wiki has
> > not been updated as I understand Xen 4.0 release is just around the
> > corner!):
>
> I'm pretty sure the Debian kernel is pvops based, so any caveats or
> limitations of one apply to the other.
>
> J
>
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-M

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