WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Re: [Xen-users] Max. PV and HVM Guests

On Mon, Nov 09, 2009 at 08:01:00PM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
>    No, I didn't limit dom0 memory in grub.conf.
> 

You should. 

If dom0 has all the memory at boot time, you need to balloon down dom0 
memory every time you create a new guest - this can (and will) cause 
problems with the dom0 linux kernel.

Linux calculates some internal parameters/buffers/values based on the
_boot time_ amount of memory. And when the amount of memory goes down to
only a small fraction of that while creating new guests bad things can
happen..

It still shouldn't crash though.. I bet your problem will get fixed when
you limit the dom0 memory to say dom0_mem=512M and reboot.

-- Pasi

>    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: [1]http://teo-en-ming-aka-zhang-enming.blogspot.com
>    My Secondary Blog: [2]http://enmingteo.wordpress.com
>    My Youtube videos: [3]http://www.youtube.com/user/enmingteo
>    Email: [4]space.time.universe@xxxxxxxxx
>    Mobile Phone (Starhub Prepaid): +65-8369-2618
>    Street: Bedok Reservoir Road
>    Country: Singapore
> 
>    On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <[5]pasik@xxxxxx> 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][6]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
> 
> References
> 
>    Visible links
>    1. http://teo-en-ming-aka-zhang-enming.blogspot.com/
>    2. http://enmingteo.wordpress.com/
>    3. http://www.youtube.com/user/enmingteo
>    4. mailto:space.time.universe@xxxxxxxxx
>    5. mailto:pasik@xxxxxx
>    6. http://www.youtube.com/watch?v=LbLaPpwNAx4

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>