Re: [Xen-devel] out-of-memory problem when restoring ballooned domains

[Lars Rasmusson <Lars.Rasmusson@xxxxxx>]

It seems to compute it just right...


# xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----    330.2        
t1                19      128    0  -b---      0.0    9619
t2                20      128    1  -b---      0.0    9620

# xm info
system                 : Linux
host                   : hpl1-024-01-eth0.hpl.hp.com
release                : 2.6.10-xen0
version                : #1 Thu Mar 10 09:42:16 PST 2005
machine                : i686
cores                  : 2
hyperthreads_per_core  : 1
cpu_mhz                : 1000
memory                 : 2047
free_memory            : 1639

# xm restore t3.saved
Error: 1

# xm save t1 t1.saved
# xm save t2 t2.saved
# xm restore t3.saved

# xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----    347.4        
t3                22      128    0  -b---      0.0    9622


So all domains have 128 Mb, and xen seems to count the memory fine...

(FYI I'm using xen-2.0-testing, checked out from bitkeeper this morning)


On Thu, 2005-03-10 at 18:39 +0000, Mark Williamson wrote:
> Can you show us the output of xm list after the restore failure?  It'd be 
> interesting to see how much memory Xen thinks the domains are occupying.
> 
> Cheers,
> Mark
> 
> On Thursday 10 March 2005 18:42, Lars Rasmusson wrote:
> > Hi,
> >
> > I have a problem with the balloon functionality.
> >
> > I have a 2G memory machine (with 2 CPUs).
> >
> > I want to create three (or more) user domains,
> > each configured to have 2G (or 1800MB) of RAM,
> > but ballooned down to 128 MB.
> >
> > The reason is that I want to be able to change the
> > size of the balloons during run time, and I want
> > each of the domains to be able to potentially get
> > all (or almost all) of the memory.
> >
> > I first create the domains t1, t2, and t3:
> >
> > xm create t1 memory=1800
> > xm balloon t1 128
> > # wait until the balloon is inflated
> > xm save t1 t1.saved
> >
> > and repeat for t2 and t3.  Notice that I can
> > create the domains with maximum memory since
> > the other domains are not using any RAM at
> > the time.
> >
> > Here comes my problem:
> >
> > When I do
> >
> > xm restore t1.saved
> > xm restore t2.saved
> > xm restore t3.saved
> >
> > I get "Error: 1" when I create the third
> > domain.  I get the feeling it has something to
> > do with "not enough memory" (is that  correct?)
> >
> > So even though the three 128 Mb domains should
> > fit easily within the approx 2G RAM, Xen doesn't
> > think so.  Which is why I've come to think there
> > might be some problem with how it is counting available RAM.
> >
> > - Is Xen taking ballooned memory into account properly?
> >
> > - Is it interpreting the info in the .saved file correctly?
> >
> > If that is the bug, I then wonder why I'm able to get two
> > user domains up and running, and not just one...
> > Could that be related to that the machine is a 2 CPU machine?
> >
> > Well that's just speculation... Does anyone have any
> > suggestions what I might be doing wrong, or where the
> > problem may be?
> >
> > Cheers,
> > Lars Rasmusson
> >
> >
> >
> >
> >
> >
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