Re: [Xen-users] dom0 freezes under high IO load - HP ML150 G2

[Daniel Mealha Cabrita <dancab@xxxxxxxxxxxx>]

Em Sáb 03 Mar 2007 03:12, você escreveu:
> You don't believe that *testing* is a good thing?
>
> I'm pretty sure the Xen documentation points out that Dom0 is not
> particularly special, except that it is privileged to manipulate DomUs.
>
> I'd love to hear other's opinions on this topic. Should Dom0 be
> entirely free of disk I/O?

I think that the every sysadmin should be able to use dom0 as seem fit.
I don't think it's a good idea running things there, but that kernel is 
expected to be fully functional. Security is another matter.

But I've already had the need for dom0 heavy disk IO while transferring files 
in order to fix a collapsed domU and dom0 crashed, taking 6 VMs with him.

> I have a job that runs every five minutes to grab CPU utilization,
> and writes that to disk. That job doesn't cause destabilization. My
> problem seems to be related to kernel SLAB corruption, which is why I
> mentioned this as something to test, and made it clear that in my
> case, it made the machine unstable.

Now that you mentioned that possibility, it could explain a Xen-related 
problem I'm experiencing with another hardware.

It's heavy IO-related too.
In this case is a Dell Poweredge 1800.

Instead of just freezing as the HPs, at some point the machine reaches the 
point it has no memory and the kernel starts killing processes (typically 
SSHd and iozone). It seems to be back to normal after that (until you start 
another stress test).
At first I thought it was an iozone bug (it allocates lots of memory anyway), 
but the problem does not happen using non-Xen kernels.


-- 
 Daniel Mealha Cabrita
 Divisao de Suporte Tecnico
 AINFO / Reitoria / UTFPR
 http://www.utfpr.edu.br

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