Re: xl vs. xm, possible bug in xl

[David Vrabel <david.vrabel@citrix.com>]

On 08/09/11 18:07, Konrad Rzeszutek Wilk wrote:
> On Thu, Sep 08, 2011 at 06:42:12PM +0200, Sven Köhler wrote:
>> Hi,
>>
>> xl is supposed to superseed xm, is this correct? How mature is xl,
>> actually? I'm asking, because the maintainers of the gentoo's xen
>> packages are migrating the init.d-scripts from xm to xl, but xl is
>> causing a lot of trouble.
>>
>> Well, xl basically fails to start domains on my system.
>>> # xl create /etc/xen/xen-sk1
>>> Parsing config file /etc/xen/xen-sk1
>>> libxl: error: libxl.c:2145:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>>> libxl: error: libxl.c:2145:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>>> libxl: error: libxl.c:2145:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>>> failed to free memory for the domain
>>
>> Consider, that autobaloon=1 in xl.conf.
>> With the autobaloon=0 the errors change to
>>
>>> # xl create /etc/xen/xen-sk1
>>> Parsing config file /etc/xen/xen-sk1
>>> libxl: error: libxl_device.c:476:libxl__wait_for_device_model Device Model not ready
>>> xl: fatal error: libxl_create.c:535, rc=-1: libxl__confirm_device_model_startup
>>
>>
>> Note, that I use dom0_mem=512M in grub.conf. Also, xm top states, that
>> there are 2139432k free memory. Considering the first issue, it seems
>> like xl is trying to baloon memory away from dom0, which fails - which
>> seems obvious wrong considering that I use dom0_mem. CONFIG_XEN_BALLOON
>> is enabled for dom0
> 
> Yeah, there is a bug there (in Linux kernel) that just got integrated in 3.1-rc5.
> Will show up in 3.0.5.
> 
> Hm, but the migrating memory away from dom0 seems bizzare. Lets ping
> David who has been in the thick of this. I have a feeling it is the
> "delta" patches ..

This patch:

http://lists.xensource.com/archives/html/xen-devel/2011-08/msg00813.html

is only relevant if the initial number of pages overlaps with gaps in
the memory map (typically more than 3 GB).  With dom0_mem=512M you
shouldn't be hitting this. So I don't think any of the patches in that
series are relevant here (but you could give them a try anyway).

>> The second issue sounds more severe, and I'm pretty clueless.
>>
>> Is this a bug in xl?
> 
>> Starting the very same domain with xm works without a hassle.
>>
>>
>> dom0:
>> vanilla 3.0.0 with vga patch
> 
> You could upgrade to 3.0.4 and then you get the VGA patch for free
> (and some bug-fixes too).
> 
>> xen 4.1.1
>>
>> domU config:
>> kernel = "/usr/src/linux-domU/_domU/vmlinux"
>> memory = 2048
>> vcpus = 8
>>
>> root = "/dev/xvda1"
>> extra = "ro"
>>
>> disk = [
>> 	"phy:/dev/md2,xvda1,w",
>> 	"phy:/dev/md5,xvda2,w",
>> ]
>> vif = [
>> 	"bridge=xenbr0,mac=00:16:3E:00:00:01",
>> 	"bridge=xenbr1,mac=00:16:3E:00:01:01",
>> ]