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

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?

Now, I should make it clear, I'm a big supporter of Dom0 doing essentially nothing. Yet, I'm also a supporter of not having difficulty sleeping at night, afraid that Dom0 might write a block or two to its own disks...

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.

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On Mar 2, 2007, at 9:58 PM, TMC wrote:

I am not sure if testing like this in Dom0 is a good thing.  Dom0 is
"special" and should not run any precesses that hit disk hard. thats
the job for DomU

Regards
TMC

On 03/03/07, Tom Mornini <tmornini@xxxxxxxxxxxxxx> wrote:
Hello Daniel.

We've had similar problems, but have received very little feedback
from our machines.

Our setup is also not entirely similar to yours. :-)

Could you try something out?

Set a cron job to run every 1 minute:

   cat /proc/slabinfo >> /root/slabinfo.txt

When we do this, our problem gets *much* worse. I'd love to know if
these are similar problems.

--
-- Tom Mornini, CTO
-- Engine Yard, Ruby on Rails Hosting
-- Reliability, Ease of Use, Scalability
-- (866) 518-YARD (9273)

On Mar 2, 2007, at 7:27 PM, Daniel Mealha Cabrita wrote:

>
> hi there,
>
>
> Does anyone have have suggestions on how to proceed in this case?
>
>
> I've experiencing dom0 (xen 3.0.3, xen-3.0.4 and 3.0.4- testing)
> lockups under
> heavy disk load (testing under dom0 directly).
> The hardware is a HP ML150 G2 with a HP 4ch SATA fakeraid (OEM
> Adaptec 1420SA,
> sata_mv driver).
> The machine does not respond to network, keyboard not anything
> noticeable
> when it happens.
>
>       I've tried passing a number of parameters to kernel but no
> success. The ones
> below even make things worse, causing a CPU0 soft lockup during boot:
> kernel = (hd0,0)/xen-3.0.4 dom0_mem=384M acpi=off noapic nolapic
>
>       The disks runs in Linux kernel RAID5. High load to/from an
> individual disk
> (the max an individual SATA HD can handle) does not cause any problem.
>
> Also, I've noticed that just after booting the machine does not
> respond to
> pings nor anything from the network. If I locally ping from that to
> another
> host, the network starts working. OR, if I wait enough time (several
> minutes), the machine's network starts to respond normally.
>
> I've got no soft lockups logged in /var/log/messages. Nor anything
> strange
> enough to call my attention.
>
>       The problem does not happen with a non-Xen kernel.
> The machine firmware (BIOS if you like) is updated to the latest
> version.
> Disabling all the non-essential hardware (USB, serial/ parallel
> ports, IDE
> ports, powersaving etc) makes no difference.
>
>       When not under high disk load the machine seems stable, with
> several domU VMs
> running happily under it.
>
> --
>  Daniel Mealha Cabrita
>  Divisao de Suporte Tecnico
>  AINFO / Reitoria / UTFPR
>  http://www.utfpr.edu.br
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users


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