[Xen-users] Questions on memory allocation

[Javier Bertoli <javier@xxxxxxxxxxx>]

Hi all,

  I'm trying to tune some memory parameters in my dom0 and domUs, and got 
stuck. I've been googling, but can't find something "straightforward" ;)
  I have a dom0 with 2GB RAM, and have 5 domUs in it, using Xen 3.1.0 with 
kernel 2.6.18, all installed through Debian packages.
  My dom0 is launched with

xenhopt=dom0_mem=256MB

  in grub's /boot/grub/menu.lst.

  I've created all my domUs with the following memory parameters:

----
memory  = '128'
maxmem  = '1024'
shadow_memory = 8
----

  My domUs have a swap partition, and I've setted the kernel's swappiness 
to 0.
  With this config, I understand that the domUs will be started with an 
starting amount of 128 MB RAM, and they will grow the amount used 
according to their needs and availability. Well. No. They begin swapping 
:/
  In one domU, that is using almost all the initial memory, when disabling 
the swap and launching another process, the OOM killer start killing 
processes.
  I've read something about a "balloon driver" that should do the magic, 
but it all refers to info prior to 2006. In a chat script someone said 
that it is now handled with the "mem-set/mem-max" parameters. There was 
also some other guy telling about /proc/xen/balloon, but couldn't find any 
detailed info on that either.
  By now, I'm suspicious that I've missunderstood the memory handling in 
Xen :)
  Can you tell me if xen dom0/domUs CAN really dynamically allocate memory 
to the domUs on demand? If so, is there any documentation I can read to 
config it properly? do I need to run any application in the domXs?
  Any help, any lead, any clue, will be greatly appreciated :)))))

  Thanks in advance

                Javier, a.a.t.

--
   "The Universe we observe has precisely the properties we should
 expect if there is, at bottom, no design, no purpouse, no evil, no
 good, nothing but blind, pitiless indiference."
                                                       (Richard Dawkins)

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