[kernel-xen] balloon messages from latest kernel-xen

[Glenn Enright]

On 19/03/13 23:50, Steven Haigh wrote:
> On 19/03/13 16:18, Glenn Enright wrote:
>> HI there,
>>
>> I'm seeing messages like the following in dmesg using the latest 3.8 
>> kernel
>>
>> System RAM resource [mem 0x28000000-0x2fffffff] cannot be added
>> xen_balloon: reserve_additional_memory: add_memory() failed: -17
>>
>> This is on an older Core2 intel MB with only 4G RAM. Everything appears
>> to be working normally otherwise. I also see some notes about a similar
>> case at 
>> http://lists.xen.org/archives/html/xen-devel/2012-12/msg01606.html
>>
>> I have autoballoon=0 in xl.conf per
>> http://wiki.xen.org/wiki/Xen_4.2_Release_Notes and the grub line
>> includes dom0_mem, eg
>>
>>         kernel /xen.gz dom0_mem=max:600M dom0_max_vcpus=1 dom0_vcpus_pin
>
> You've turned ballooning off, but you've got it on in the hypervisor.
>
> Use this instead:
>     kernel /xen.gz dom0_mem=600M dom0_max_vcpus=1 dom0_vcpus_pin
>

Thanks Steven, that makes sense. But... if I do that I find there is a 
bunch or RAM that dom0 can no longer use.

3.6.10 > dom0_mem=max:600M
DirectMap4k:      614792 kB
DirectMap2M:           0 kB

test1 3.8.3-1 > dom0_mem=max:600M
DirectMap4k:      614792 kB
DirectMap2M:           0 kB
noise messages in kernel log from xen_balloon (perhaps those were just 
silent before?)

test2 3.8.3-1 > dom0_mem=600M
DirectMap4k:     4119552 kB
DirectMap2M:           0 kB

That is a pretty big difference on test2. I've tried a bunch of 
different command line combos, but nothing seems to free up that RAM and 
silence the log noise at the same time.

Is there any other option to administratively disable ballooning on the 
command line? Not seeing anything on 
http://xenbits.xen.org/docs/unstable/misc/xen-command-line.html

Regards, Glenn