Re: [Xen-users] dom0 memory usage >1GB at startup (no domU's configured)

[Markus Hochholdinger <Markus@xxxxxxxxxxxxxxxxx>]

Hello,

Am 04.04.2010 um 04:44 Uhr schrieb stalks <xen-users@xxxxxxxxxxxxxxxxxx>:
> I have a new install of Debian Squeeze.
> I have followed the hints from the ParaVirtOps wiki page to grab
> Jeremy's kernel sources from kernel.org and compiled a 2.6.31.x (and
> 2.6.33.x) kernel.

you could also install the debian kernels:
  http://packages.debian.org/sid/linux-image-2.6.32-4-xen-686
or
  http://packages.debian.org/sid/linux-image-2.6.32-4-xen-amd64


> I have yet to install any significant software other than package
> "xen-hypervisor-3.4-amd64".
> The machine is a Core i7 920 with 8GB RAM.
> If I boot the plain kernel (without xen-3.4.gz) I get ~65MB ram usage
> shown in free -m.
> If I boot with full xen, bear in mind I have no domU's yet, I get the
> following:
>  > free -m
>               total       used       free     shared    buffers     cached
> Mem:          7948       1412       6535          0          9        107
> -/+ buffers/cache:       1295       6652
> Swap:            0          0          0
>  > xm info
> host                   : oracle
> release                : 2.6.33.2-amd64-xen
> version                : #1 SMP Sun Apr 4 00:21:54 BST 2010
> machine                : x86_64
> nr_cpus                : 8
> nr_nodes               : 1
> cores_per_socket       : 4
> threads_per_core       : 2
> cpu_mhz                : 2660
> hw_caps                :
> bfebfbff:28100800:00000000:00000340:0098e3bd:00000000:00000001:00000000
> virt_caps              : hvm
> total_memory           : 8183
> free_memory            : 2174
> node_to_cpu            : node0:0-7
> node_to_memory         : node0:2174
> xen_major              : 3
> xen_minor              : 4
> xen_extra              :
> 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          : unavailable
> cc_compiler            : gcc version 4.4.3 (Debian 4.4.3-2)
> cc_compile_by          : waldi
> cc_compile_domain      : debian.org
> cc_compile_date        : Mon Mar  1 21:16:18 UTC 2010
> xend_config_format     : 4
>  > xm top
>      xentop - 03:33:21   Xen 3.4
>      1 domains: 1 running, 0 blocked, 0 paused, 0 crashed, 0 dying, 0
> shutdown
>      Mem: 8379516k total, 6152576k used, 2226940k free    CPUs: 8 @ 2660MHz
> (free -m): Over 1GB used inside dom0 already?

It's possible that some drivers or programs are preserving memory as 
percentage of the whole memory it sees.


> (xm info): Only 2GB available for guests?
>   (xm top): Over 6GB used?

Sure? Tried to start a domU with 3GB RAM? It seems this is the auto balooning 
of the dom0. It works as follows: Take the whole memory for dom0 and give 
away memory if domUs need them, e.g. when starting a new domU.
I prevent this with
  (dom0-min-mem 0)
in my /etc/xen/xend-config.sxp and giving
  dom0_mem=256M
as parameter to the hypervisor in my grub config, this looks like this for me:
title           Xen 3.4-amd64 / Debian GNU/Linux, kernel 2.6.32-4-xen-686
root            (hd0,0)
kernel          /boot/xen-3.4-amd64.gz dom0_mem=256M
module          /boot/vmlinuz-2.6.32-4-xen-686 root=/dev/md0 elevator=deadline 
ro pci=nomsi console=tty0
module          /boot/initrd.img-2.6.32-4-xen-686


> The only processes running outside of bare minimum are xinetd, sendmail,
> mdadm and ssh.
> I can stop xend and xendomains from starting, and I still have 1GB used
> at startup.
> The same setup on a lesser spec'd machine is working fine with ~140Mb
> used at boot. I've spent a few hours on this and am at a loss.

Try to limit the memory for your dom0 as seen above and look again.


> Some info can be found at the following sources:
> http://www.nooblet.org/other/xen-users/lspci.txt
> http://www.nooblet.org/other/xen-users/lspci-vv.txt
> http://www.nooblet.org/other/xen-users/cpuinfo.txt
> http://www.nooblet.org/other/xen-users/grub.txt
> http://www.nooblet.org/other/xen-users/dmesg.txt
> http://www.nooblet.org/other/xen-users/meminfo.txt
> http://www.nooblet.org/other/xen-users/ps-awwux.txt
> Someone show me the light!


-- 
greetings

eMHa

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