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Re: [Xen-devel] [BUG] invocation of xl create with insufficient memory for new domU causes system reboot


  • To: xen-devel@xxxxxxxxxxxxx
  • From: "Georgy V. Repin" <grep@xxxxxxxxxxxx>
  • Date: Wed, 02 Apr 2014 09:47:24 +0400
  • Delivery-date: Wed, 02 Apr 2014 08:01:23 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>



01.04.2014 14:17, Georgy V. Repin ÐÐÑÐÑ:

01.04.2014 13:52, Ian Campbell ÐÐÑÐÑ:
On Tue, 2014-04-01 at 13:35 +0400, Georgy V. Repin wrote:
Hello!

1. Problem: invocation of xl create when there is not enough memory to
create new domU causes oom to select process to kiill; when oom selects
to kill quemu-system-* process, this causes kernel panic (it's my
suppose, because i see no message "kernel panic" in log, but i do see
"CPU: 0 PID: 7899 Comm: qemu-system-i38 Not tainted 3.10.17-gentoo #1" +
failed call trace), and, therefore (assuming default settings) kernel
reboot (see log at "4.")
Couple of remarks:
- fix checking of available memory for new domU in xl toolstack could
serve as workaround
- real cause is not clear to me, maybe it's not even a xen bug (quemu ?
kernel ?)

Are you using dom0_mem= together with auto ballooning enabled in the
toolstack?

informika-xen-3 ~ # cat /proc/cmdline
placeholder root=/dev/sda1 ro

part of grub.cfg

                 if [ "$grub_platform" = "pc" -o "$grub_platform" = ""
]; then
                     xen_rm_opts=
                 else
                     xen_rm_opts="no-real-mode edd=off"
                 fi
             multiboot    /boot/xen-4.gz placeholder   ${xen_rm_opts}
             echo    'Loading Linux 3.10.17-gentoo ...'
             module    /boot/vmlinuz-3.10.17-gentoo placeholder
root=/dev/sda1 ro

xl.conf:
# Control whether dom0 is ballooned down when xen doesn't have enough
# free memory to create a domain.  "auto" means only balloon if dom0
# starts with all the host's memory.
#autoballoon="auto"

So:
     - no dom0_mem= as boot param
     - autobaloon is set to default ("auto", i suppose)

Any other suggestions what to "do" with this "bug" ?
(Captain Obvious definetly says "you should not start new domU when you don't have enough memory")



I think it was Xen 4.4 which gained the ability to detect dom0_mem= and
disable ballooning automatically in that case, but I might be
misremembering.

Ian.



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