Re: [Xen-users] understanding dom0 usage memory

[Claudinei Matos <claudineimatos@xxxxxxxxxxxxxxxxx>]

Stephan Seitz wrote:
> Claudinei Matos schrieb:
> > Hi guys,
> > My question is if the xen kernel part do try to allocate memory which 
> > I can't see on ps/top utils or if I maybe have a problem with my 
> > machines setup?
> > Another question is if it's OK to just allocate 128MB to dom0? As I 
> > said the only machine with 128MB is a test machine which is not used 
> > this much.
> The dom0 memory shown by "free" has nothing to do with your physical ram.
> By default, dom0 gets all memory which is not used by domU's.
> If you're starting domU's your dom0 memory will shrink until dom0_min_mem
> (see xm help, man xm ...). The same way your dom0 memory probably 
> balloons
> out if you're stopping domU's.
> If you want a static ram size at dom0, you need to add dom0_mem, 
> dom0_max_mem
> and/or dom0_min_mem parameters to your grub entry (after xenXXX.gz).
I'm already using boot option "dom0_mem" to limit the physical ram usage 
on all my nodes as well as the xend-config.sxp "dom0_min_mem" parameter 
with the same value of "dom0_mem" boot option.
I still in doubt about if xen kernel modules are using the free memory 
but not showing up its use at top and ps commands.
For tests purpose I've realized that none of the xen visible process do 
care about the domU "life". I can kill some xen process and the domU 
still running (I did not tested with blktapctrl as I think it can give 
some problems with domU storage). So I wonder there's some kernel land 
process (invisible to ps/top) which care about domU and who's probably 
consuming some free memory. Is there an away to see such a process 
and/or even look at its memory usage?

Thanks,

Claudinei Matos

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