Xen users - Feb 2007 - Problem with dom0_mem and tmpfs on SLES10

Hello friends!

In this week, i had a problem with Xen version 3.0.2_09749-0.7 on SLES10 for
x86, when
the initrd-xen file was loaded. On console, various messages about "No
space
left on device"
appears later that the "/dev" was monted on a tmpfs filesystem (for
udev).

The only sollution for this problem at that moment, was remove the
"dom0_mem=192M" and the
"mem=1024M of my GRUB configuration file (menu.lst on SuSE).

My dom0 configurations are:

- Intel(R) Xeon(TM) CPU 2.80GHz
- 1 GiB RAM

grub:
title XEN
    root (hd0,0)
    kernel /xen.gz dom0_mem=192M
    module /vmlinuz-xen root=/dev/system/root vga=0x314
resume=/dev/system/swap  splash=silent showopts acpi=off apm=off mem=1024M
    module /initrd-xen


df command output:
 # df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/system-root
                       2097084   1717340    379744  82% /
udev                    481016       292    480724   1% /dev
/dev/sda1               256666     23426    219988  10% /boot
/dev/mapper/system-var
                       2097084    174604   1922480   9% /var


# xm dmesg:
(attached file) :-)

# rpm -q udev:
udev-085-30.10

# uname -a:
Linux omega 2.6.16.21-0.15-xen #1 SMP

The problem was resolved, but I need to understand if this is a "bug"
on Xen
/ udev, or
I made a mistake configuration.

Looking for bug reports, I don''t found none report bug related with
this...


Thanks!!!! :-)

-- 
André Luiz da Silva



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On 2/1/07, Andre Luiz da Silva <andrack@gmail.com>
wrote:
> Hello friends!
>
> In this week, i had a problem with Xen version 3.0.2_09749-0.7 on SLES10
for
> x86, when
> the initrd-xen file was loaded. On console, various messages about "No
space
> left on device"
> appears later that the "/dev" was monted on a tmpfs filesystem
(for udev).
Do you talk about booting the dom0 or domU machine?
>
> The only sollution for this problem at that moment, was remove the
> "dom0_mem=192M" and the
> "mem=1024M of my GRUB configuration file (menu.lst on SuSE).

In my experience, it is problematic to use suse with not enough
memory, and 192 might be not enough. So that''s why you probably needed
to remove the dom0_mem option. Maybe they try to create some ramdisk
that is just too small for the unpacked initrd to fit in - can''t you
see exactly what the messages say which filesystem is full?

I am not sure what the mem=1024 option is exactly doing, I can imagine
two problems:
1) it could conflict with the dom0_mem=192 - you basically tell xen to
give the dom0 only 192, but tell the dom0 kernel he has 1024 MB, that
doesn''t match
2) if all the 1024 MB are used by dom0 linux, so what memory do you
want to use in domU?

Apart from that, using too much memory can also be a suse-specific
problem, and you should probably ask their support.

Henning

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