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Re: [Xen-users] with heavy VM IO, clocksource causes random dom0 reboots

On Mon, Aug 29, 2011 at 8:37 AM, Benjamin Weaver
<benjamin.weaver@xxxxxxxxxxxxx> wrote:
> On Debian Squeeze (2.6.32-5) running Xen 4.0, I have created 2 Ubuntu Lucid
> Lynx (Ubuntu 10.04) vms. The vms, in a stress test, pass a large file
> between them via nfs file sharing. A previous entry in this forum helped to
> establish that some ethernet cards improve VM IO performance.
> However, our box installed with better intel nics is still rebooting under
> heavy VM IO loads. The kernel call trace is copied below. Note the first
> line, a reference to PV clocksource
> note: these bug notices
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=603727
> and this suggestion page:
> http://wiki.xensource.com/xenwiki/xenpm#head-253cbbe6cf12fa31e10022610cd7090aa980921f
> These pages, (the last, in particular) describe IO jitter related to
> clocksource. This would be consistent with the problems with interrupts we
> have been experiencing.
> 1. I have been told to set clocksource=pit on dom0. How and where, in
> Squeeze is this clocksource parameter set? At compile time, or at boot time?
> And if at boot time, in /etc/default/grub?
> How exactly, if in /etc/default/grub, is this parameter set. Lines in that
> file begin with capital letters:
> GRUB_CMDLINE_XEN="com1=9600,8n1 console=com1,vga noreboot"
change this line to:
GRUB_CMDLINE_XEN="com1=9600,8n1 console=com1,vga clocksource=pit noreboot"

> GRUB_CMDLINE_LINUX="console=tty0 console=hvc0"
> 2. Is a package necessary for pit ?
You shouldn't. Do like the wiki says and check
xm dmesg | grep -i timer

> 3. should clocksource = pit be set on domUs as well?
Based on what I am reading from the wiki. It looks like it is a Xen
hypervisor setting, so no.

Hope that helps.


Todd Deshane

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