Re: [Xen-devel] Memory allocation going seriously wonky on 4.1.1

[Anthony Wright <anthony@xxxxxxxxxxxxxxx>]

On 01/10/2011 13:07, Pasi Kärkkäinen wrote:
> On Fri, Sep 30, 2011 at 04:07:06PM +0100, Anthony Wright wrote:
>> I have a machine with 16GB of RAM running 32 bit xen 4.1.1 with Dom0
>> running a 3.0.4 linux kernel and 23 paravirtualized DomUs.
>>
> Hey,
>
> Why 32bit Xen? I think all (most?) hypervisor testing happens with 64bit Xen.
> Note that you can still have 32bit dom0 kernel with 64b hypervisor.
I'm going to investigate 64 bit xen on a 32 bit Dom0 soon, but as to the
32 xen, I work quite a lot with older hardware and Xen since it does
paravirtualisation, and it's a really good way to re-use old hardware.
>> As the free ram gets to 2391 MB free the system behaves as if it's got
>> no more ram, and starts grabbing ram from Dom0, before getting even more
>> confused and failing to start DomUs and eventually crashing the whole
>> machine. I have attached a tarball with the output of xl dmesg, xl info
>> & xl list at various points.
>>
> - Do you use dom0_mem= parameter for Xen? 
> - Did you disable dom0 ballooning? 
>
> http://wiki.xen.org/xenwiki/XenBestPractices
I was already using the dom0_mem= parameter on the xen hypervisor, but I
disabled dom0 ballooning (enable-dom0-ballooning no), and just for good
measure I also set (dom0-min-mem 2000). This had no effect, when I
increase the 10-4 memory requirements, on restart the Dom0 memory is
reduced to 1713MB and xl info reports 2391MB free.
>> Stage 1
>> Everything is fine, Dom0 has 2000MB according to xl list, and 'xl info'
>> says there is 2405MB free.
> - How much memory did dom0 initially have? 
> - Did you use mem= parameter for dom0 kernel (vmlinuz) ?
>
> See: http://wiki.xen.org/xenwiki/Linux_30_bugs
dom0 starts with 2000MB.
I didn't use mem= on the linux kernel - I thought it wasn't neccessary.


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