Re: [Xen-users] Problem for "xm create": "kernel: Setting mem allocation to ..."

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > there is a balloon setting to specify the ram usage by Dom0, look in your
> > /etc/xend-config.sxp near the end of the file.
>
> Not here (SLES10): I only have:
> # Dom0 will balloon out when needed to free memory for domU.
> # dom0-min-mem is the lowest memory level (in MB) dom0 will get down to.
> # If dom0-min-mem=0, dom0 will never balloon out.
> (dom0-min-mem 196)

That's the one you'll want to tweak if you're using autoballooning to reduce 
dom0 when creating other domains (as opposed to statically choosing dom0's 
size at boot time / or ballooning dom0 manually with xm mem-set).

> > Your error msg indicates there is not enough free ram.
>
> not very clearly, and I wonder why it takes about one minute to find out
> that there's not enough  RAM.

Some of the error messages aren't very clear :-/

> > You can check it with xm list, that will show the current mem usage with
> > Xen. Free -h will show system mem usage.
>
> # free -h
> free: invalid option -- h
> [...]

Now this is something I *always* get wrong myself.

I think the OP meant to say "free -m" for free space in megabytes.  It's easy 
to muddle this up with the "df -h" command for "free disk space, human 
readable (i.e. megabytes) - I confuse the two very frequently.

"xm info" will tell you about the free memory in the system, from Xen's PoV 
(i.e. what you have available for domain creation)

Cheers,
Mark

> Ulrich
>
> > On 10/19/06, Ulrich Windl <ulrich.windl@xxxxxxxxxxxxxxxxxxxx> wrote:
> > > Hi,
> > >
> > > When trying to boot a freshly created VM, nothing seems to happen, but
> > > Dom0
> > > repeats  messages like
> > > kernel: Setting mem allocation to ... kIB
> > > while "..." is some large number like this:
> > > Oct 19 15:55:33 rkdvmso1 kernel: Setting mem allocation to 816764 kiB
> > > Oct 19 15:55:41 rkdvmso1 kernel: Setting mem allocation to 816764 kiB
> > > Oct 19 15:55:46 rkdvmso1 kernel: Setting mem allocation to 816764 kiB
> > > Oct 19 15:55:54 rkdvmso1 kernel: Setting mem allocation to 816764 kiB
> > >
> > > Eventually I see (after "xm create"):
> > > Error: The privileged domain did not balloon!
> > >
> > > Now I think the error message on the console and in the syslog could be
> > > improved:
> > > Is Dom0 kernel retrying, how much is available (I assume less than
> > > demanded).
> > > Could this be a NUMA problem?
> > >
> > > A "# xm mem-set 0 256" to reduce the mem of Domain-0, but the VM
> > > wouldn't start,
> > > and Domain-0 re-allocated the previous size (556M)
> > >
> > > How do I limit the maximum mem for Domain-0, so that DomUs have enough
> > > RAM left
> > > over for them?
> > >
> > > Regards,
> > > Ulrich
> > >
> > >
> > > _______________________________________________
> > > Xen-users mailing list
> > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-users
>
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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