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Re: Xen support on Squeeze

On 2010-04-06, micah anderson wrote:
> On Thu, Apr 01, 2010 at 03:40:40PM -0400, Micah Anderson wrote:
> > "Nikita V. Youshchenko" <yoush@debian.org> writes:
> > 
> > >> We have had to carry that patch without any upstream support (or sharing
> > >> with Novell, which eventually released SLES 11 with 2.6.27).  As a
> > >> result, the xen-flavour kernels for lenny are very buggy, particularly
> > >> for domains with multiple vCPUs (though that *may* be fixed now).
> > >
> > > Unfortunately it is not fixed.
> > >
> > > We here once migrated to xen and now rely on it, and that gives lots of 
> > > frustration. For any loaded domain we still have to run etch kernel, 
> > > because lenny kernel constantly crashes after several days of heavy load. 
> > > Dom0's run lenny kernel - and with a fix for #542250 they don't crash, but 
> > > those are almost unloaded.
> > 
> > I was having problems with multiple vCPUs also, under moderate load I
> > would regularly get crashes. I reported my findings in #504805. I
> > swapped out machines, didn't work. When the fix for the xen_spin_wait()
> > came out, I eagerly switched to that, but it didn't fix my problem. I
> > even tried my hardest to switch to the latest upstream Xen kernel to see
> > if that would fix things, but it was way too unstable and I couldn't get
> > it to work at all.
> > 
> What do you exactly mean with the 'upstream Xen kernel' ?

The latest xen-kernel, not from Debian. There are a number of them, the
Novell/OpenSuse forward-port of the old-style xenlinux patches, and the
pvops dom0 git tree. The pvops one was the one I was trying to get
working since the other versions of the kernel aren't receiving any
attention and all dev is happening in the pvops.

> > Eventually I stumbled on a way to keep my machines from restarting, its
> > not a great solution, but it stops me from having to deal with the
> > failure on a daily basis. I think that anyone else who is having this
> > problem can do this and it will work. Obviously this is not the right
> > solution, but it works until we can get a fix.
> > 
> > First I made sure this was set:
> > 
> > /etc/xen/xend-config.sxp: (dom0-cpus 0)
> > 
> > Then I pinned individual physical CPUs to specific domU's, once pinned,
> > the problem stops.
> > 
> vcpu pinning is not required for a properly working kernel..

It shouldn't be, I agree... but it seems like it is required to keep the
kernel from a daily panic.


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