Re: [Xen-devel] (XEN) page_alloc.c:1148:d0 Over-allocation for domain 0: 694017 > 694016

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.04.12 at 04:34, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> I am not sure how this is happening, but I can only reproduce this
> is I use the "max" parameter in the 'dom0_mem=*:max:*' combination:

Of course - without the ",max:" there just isn't any limit for Dom0.

> sh-4.1# xl info | grep dom0_mem
> xen_commandline        : cpuinfo dom0_mem=1G,max:2711M cpufreq=verbose 
> com1=115200,8n1 console=com1,vga loglvl=all guest_loglvl=
> 
> 
> 02:32:22 # 19 :/sys/devices/system/xen_memory/xen_memory0/ 
>> cat /proc/meminfo |grep Direct
> DirectMap4k:     2776516 kB
> DirectMap2M:           0 kB
> 
> 02:33:11 # 23 :/sys/devices/system/xen_memory/xen_memory0/
>> echo 2776516 > target_kb
> 
> (XEN) page_alloc.c:1148:d0 Over-allocation for domain 0: 694017 > 694016
> (XEN) memory.c:133:d0 Could not allocate order=0 extent: id=0 memflags=0 
> (239 of 256)
> (XEN) page_alloc.c:1148:d0 Over-allocation for domain 0: 694017 > 694016
> (XEN) memory.c:133:d0 Could not allocate order=0 extent: id=0 memflags=0 (0 
> of 17)
> (XEN) page_alloc.c:1148:d0 Over-allocation for domain 0: 694017 > 694016
> (XEN) memory.c:133:d0 Could not allocate order=0 extent: id=0 memflags=0 (0 
> of 17)
> 
>>
> The value that it decided it was Ok with was: 2776510kB which is 6 pages 
> short of the goal and that makes the messages disappear.

How would that be? 2711MiB = 2776064kiB, which 446k off the value
above. And apart from that, the value above isn't even divisible by 4
(i.e. not an even number of pages).

> Any ideas of what that might be? Could it be the shared_info, hypercall page,
> start_info, xenconsole and some other ones are the magic 6 pages which
> inhibit how much we can balloon up to?

Not likely: The hypercall page is in kernel (image) memory, and there's
no console page at all fro Dom0.

Jan


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