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

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)

         [    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...


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_XEN_XENBUS_FRONTEND (available since 2.6.38)
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


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