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

[Glenn Enright]

On 20/03/13 16:29, Glenn Enright wrote:
> 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
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HI all

Just following up on this, I ended up using a workaround with 
"dom0_mem=599M,max:600M" That gives me all the allocated RAM and only 
slightly less than maximum in action. And no error messages in the 
kernel. It also means I don't need to mess with proc values later in the 
boot process :).

Regards, Glenn