Re: [Xen-users] dynamic memory extension not working on Debian Squeeze

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-11-20 at 23:45 +0000, Peter Viskup wrote:
> On 11/20/2012 06:43 PM, Ian Campbell wrote:
> > On Tue, 2012-11-20 at 17:30 +0000, Alexandre Kouznetsov wrote:
> >> I have attached the complete dmesg for a better reference. This one is
> >> after I changed from "mem=8G" to "mem=8192M".
> > It's interesting that it has both:
> >          [    0.000000] BIOS-provided physical RAM map:
> >          [    0.000000]  Xen: 0000000000000000 - 00000000000a0000 (usable)
> >          [    0.000000]  Xen: 00000000000a0000 - 0000000000100000 (reserved)
> >          [    0.000000]  Xen: 0000000000100000 - 0000000010000000 (usable)
> >
> > and
> >          [    0.000000] user-defined physical RAM map:
> >          [    0.000000]  user: 0000000000000000 - 00000000000a0000 (usable)
> >          [    0.000000]  user: 00000000000a0000 - 0000000000100000 
> > (reserved)
> >          [    0.000000]  user: 0000000000100000 - 0000000010000000 (usable)
> >
> > Where I think the second one is the result of passing mem=, yet it is
> > exactly the same! I suspect it has taken the command line provided limit
> > and clamped it...
> >
> > Another thing you could try is using the memmap command line option to
> > generate a memmap like those above but with the limit on the 3rd one ==
> > 8G. You'll have to read Documentation/kernel-parameters.txt to figure
> > out exactly how though since I'm not sure how that stuff works.
> >
> > Another workaround would be to boot with 8G and then balloon down ASAP.
> > This means you need the spare RAM available to boot the guest though,
> > which isn't ideal...
> >
> > Ian.
> 
> I was just followed this wiki [1] and found that these options/features 
> are not available in Debian's domU paravirt_ops kernel (2.6.32-5-amd64):
> CONFIG_PARAVIRT_SPINLOCKS (really needed?)
> CONFIG_XEN_XENBUS_FRONTEND (available since 2.6.38)

Neither of these have any relevance to the problem at hand.

> Looks like that wiki needs rewrite and having more information about 
> every kernel option would be great. Anyway I am quite tired of checking 
> those kernel options and decided to open an bug report for it [2]. Will 
> see what will happen.
> 
> [1] http://wiki.xensource.com/xenwiki/XenParavirtOps
> [2] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=693851

I'm afraid that I'm the Debian maintainer too, and I'm still fresh out
of theories, so the above suggestions and the ones in
<1353431265.13542.83.camel@xxxxxxxxxxxxxxxxxxxxxx> are as good as it is
going to get. Sorry.

(note that wiki.xensource.com/xenwiki is the old wiki, which is no
longer maintainer. wiki.xen.org/wiki is the maintained one).

Ian.



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