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[Xen-users] Questions on memory allocation

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Questions on memory allocation
From: Javier Bertoli <javier@xxxxxxxxxxx>
Date: Tue, 30 Oct 2007 13:28:02 -0300 (ART)
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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


  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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