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

[Alexandre Kouznetsov <alk@xxxxxxxxxx>]

El 20/11/12 03:33, Ian Campbell escribió:
> On Thu, 2012-11-15 at 19:59 +0000, Peter Viskup wrote:
>
> In dmesg.2012-11-15.log I see:
> [    0.000000]  Xen: 0000000000000000 - 00000000000a0000 (usable)
> [    0.000000]  Xen: 00000000000a0000 - 0000000000100000 (reserved)
> [    0.000000]  Xen: 0000000000100000 - 0000000010000000 (usable)
>
> which indicates that the maximum RAM size the kernel can cope with is
> 0x10000000 == 256M, which matches your experience.
>
> I suspect that if you mem-set to e.g. 128M then you could increase back
> to 256M successfully.
Yes. I can confirm that behavior. The RAM size can be shrinked and grown 
correctly, but only under the limit of the initial size.
> What is missing is booting "pre-ballooned" e.g. with a maximum memory
> size of 1G but only using 256M on boot.
Some Gentoo wiki http://en.gentoo-wiki.com/wiki/Xen/Creating_DomUs says 
they get a feedback from balloon in their dmesg, like this:
xen_mem: Initialising balloon driver.

My DomU's dmesg does not mentions anything about xen_mem, but does shows 
a xen_balloon message:
xen_balloon: Initialising balloon driver with page order 0


> I'm a little bit rusty on the details but older kernels and/or toolstack
> needed a little more manual intervention. Can you try adding
> "mem=4G" (or 4092M to match your config) to your domU command-line?
In my case, same result. Tried "mem=8G" and "mem=8192M" (matching the 
config, maxmem=8192).
root@scoutapi-dev:~# dmesg| grep "Command line"
[    0.000000] Command line: root=/dev/xvda2 ro mem=8G
root@scoutapi-dev:~# dmesg | grep Xen
[    0.000000]  Xen: 0000000000000000 - 00000000000a0000 (usable)
[    0.000000]  Xen: 00000000000a0000 - 0000000000100000 (reserved)
[    0.000000]  Xen: 0000000000100000 - 0000000010000000 (usable)
[    0.000000] Booting paravirtualized kernel on Xen
[    0.000000] Xen version: 4.0.1 (preserve-AD)
[    0.000000] Xen: using vcpu_info placement
[    0.000000] Xen: using vcpuop timer interface
[    0.000000] installing Xen timer for CPU 0
[    0.009451] PCI: setting up Xen PCI frontend stub
[    0.282324] Initialising Xen virtual ethernet driver.

root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
MemTotal:         258908 kB
root@scoutapi-dev:~# cat 
/sys/devices/system/xen_memory/xen_memory0/target_kb
262144

root@on05:~# xm mem-set scoutapi-dev 512
root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
MemTotal:         258908 kB
root@scoutapi-dev:~# cat 
/sys/devices/system/xen_memory/xen_memory0/target_kb
524288

--
Alexandre Kouznetsov


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