No, I didn't limit dom0 memory in grub.conf.

Here's my xm info output after I have shutdown all the virtual machines.

[root@fedora11-x86-64-host ~]# xm list
Name                                        ID   Mem VCPUs      State
Time(s)
Domain-0                                     0  2812     2     r-----
3242.5
[root@fedora11-x86-64-host ~]# xm info
host                   : fedora11-x86-64-host
release                : 2.6.30-rc3-enming.teo-tip
version                : #1 SMP Wed Aug 19 23:14:15 SGT 2009
machine                : x86_64
nr_cpus                : 2
nr_nodes               : 1
cores_per_socket       : 2
threads_per_core       : 1
cpu_mhz                : 2800
hw_caps                :
bfebfbff:20100800:00000000:00000140:0400e3bd:00000000:00000001:00000000
virt_caps              : hvm hvm_directio
total_memory           : 6039
free_memory            : 3124
node_to_cpu            : node0:0-1
node_to_memory         : node0:3124
xen_major              : 3
xen_minor              : 5
xen_extra              : -unstable
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Tue Sep 01 11:34:31 2009 +0100 20143:a7de5bd776ca
xen_commandline        : iommu=1
cc_compiler            : gcc version 4.4.1 20090725 (Red Hat 4.4.1-2) (GCC)
cc_compile_by          : root
cc_compile_domain      : (none)
cc_compile_date        : Thu Sep 10 07:01:13 SGT 2009
xend_config_format     : 4

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    Hi,
> >
> >    Please watch this 4-minute video at
> >    [1]http://www.youtube.com/watch?v=LbLaPpwNAx4
> >
> >    I have only started 3 HVM Linux guests with 1 GB ram each. I can't
> start
> >    the 4th HVM guest. If I attempt to start the 4th instance, it will
> crash
> >    dom0.
> >
> >    Are there anything in the xm dmesg output that could explain the low
> limit
> >    to the number of VMs that I could start before dom0 becomes
> unresponsive?
> >
>
> Have you limited dom0 memory (by specifying dom0_mem=XMB option in
> grub.conf for xen.gz) ?
>
> What does "xm info" say about free memory before starting any guests?
>
> -- Pasi
>
>
>