On 08/31/2011 05:38 PM, Pasi Kärkkäinen wrote: > On Tue, Aug 30, 2011 at 03:30:46PM +0200, Dennis Jacobfeuerborn wrote: >> On 08/27/2011 09:12 PM, sylvan.dcunha at gmail.com wrote: >>> Dear Dennis, >>> >>> Thanks a lot for the wise reply.. really did boost my knowledge.. >>> honestly was unware of the fact that dom0 is just like another VM ... >>> Anyway I had never restricted dom0 mem and since my 4 vms were working fine >>> with no issues >>> i never bothered much. >> >> Yes, this is different from KVM where the VMs really are just normal >> processes on the host system and the host system itself isn't a VM. >> >> On a Xen system if you look at /etc/grub.conf you'll notice that it looks >> slightly different than on a non-virtualized system. Specifically you'll >> find the following line: >> kernel /xen.gz-2.6.18-164.el5 >> >> That's the actual hypervisor and really the host system and once started it >> will basically start dom0 and give it special privileges. So Dom0 and the >> DomU's all run on top of the actual hypervisor. >> >>> It was only after I added more 32 gb to existing 32 gb i did realise the >>> above issue.. >> >> Apparently dom0 has a 32G limit but that shouldn't be an issue unless you >> actually really require more than 32G specifically for dom0 and not the VMs. >> >>> anyway I will try to restrict my dom0 to 1 GB ... and check it out. >> >> Remember that the problems with the dynamic memory management are most >> likely fixed nowadays so the limitation is not strictly necessary. But then >> 1G will probably be more than enough for dom0 so it doesn't really hurt either. >> > > Still today you should dedicate a fixed amount of memory for dom0! > say, 1GB, or so. > > It's because of how Linux kernel allocates (and wastes) page struct memory: > http://wiki.xen.org/xenwiki/XenBestPractices Very good to know. Thanks for the information! Regards, Dennis