Re: [Xen-users] Dom0 Memory?

[Dario Faggioli <raistlin@xxxxxxxx>]

On Thu, 2012-05-10 at 14:20 +0200, Flavio wrote: 
> On 10 May 2012 12:38, Dario Faggioli <raistlin@xxxxxxxx> wrote:
> > On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
> >> > What does 'xm info' say?
> >> # xl info
> >> total_memory           : 8107
> >> free_memory            : 6968
> >>
> > So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the
> > problem?
> Yes, but as far as I can see, even if xl info gives me such values,
> the real amount
> of free RAM is very less than it declares. I've reported also the free and the
> cat /proc/meminfo output on the purpose and what I can see, practically, is 
> that
> I cannot run Chromium, or other "big" applications because of this lack of 
> free
> RAM. This is an issue that has been confirmed many months ago.
> 
Just to be sure we got each other properly, that is again fine,
as /proc/meminfo or `free' in Dom0 reports the amount of free memory in
Dom0, which is a VM to which you've given 1GB of RAM.

Then, if your Dom0 has issues (slowdowns, OOM killings, etc.) with that
amount of RAM you either should put more memory on dom0_mem= or avoid
putting the dom0_mem option at all. Of course, the wiki links tells you
shouldn't get rid of that cmdline option but, hey, one has to be free to
do what he likes on his machines! :-P

It's not hard to imagine that 1GB (unfortunately) is far less what a
modern Desktop needs to run properly. And about the latter point, if you
install the xen packages on Fedora, it does not give you any dom0_mem
option by default, so...

> Uhm, OK. So all my doubts come from the fact that, when I was using
> xen-sources (and not the vanilla (gentoo) sources), I've always seen all the
> free RAM correctly. But if you say this, I can be more pacific. ;-)
> 
That could well be true. I'm hacking on Xen from a very short while, so
I'm not going to claim it has always been like it is now! :-D

> > Hope of being of some help.
> For sure yes! I appreciate your interest.
> 
Glad to hear that. :-)

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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