memory zones and the KVM guest kernel

memory zones and the KVM guest kernel

[David Evensky]

Hi,

When I boot my guest kernel with KVM, the dmesg output says that:

...
[    0.000000] Zone PFN ranges:
[    0.000000]   DMA      0x00000010 -> 0x00001000
[    0.000000]   DMA32    0x00001000 -> 0x00100000
[    0.000000]   Normal   empty
[    0.000000] Movable zone start PFN for each node
[    0.000000] early_node_map[2] active PFN ranges
[    0.000000]     0: 0x00000010 -> 0x0000009f
[    0.000000]     0: 0x00000100 -> 0x0007fffd
...

Why is the Normal Zone empty? Is it possible to have some of the
guest's memory mapped in the Normal zone?

Is there a good reference that talks about the normal, movable,
etc. memory zones?

Thanks,
\dae

Re: memory zones and the KVM guest kernel

[Avi Kivity]

On 05/23/2011 11:19 PM, David Evensky wrote:
> Hi,
>
> When I boot my guest kernel with KVM, the dmesg output says that:
>
> ...
> [    0.000000] Zone PFN ranges:
> [    0.000000]   DMA      0x00000010 ->  0x00001000
> [    0.000000]   DMA32    0x00001000 ->  0x00100000
> [    0.000000]   Normal   empty
> [    0.000000] Movable zone start PFN for each node
> [    0.000000] early_node_map[2] active PFN ranges
> [    0.000000]     0: 0x00000010 ->  0x0000009f
> [    0.000000]     0: 0x00000100 ->  0x0007fffd
> ...
>
> Why is the Normal Zone empty?

The DMA32 zone covers the first 4GB of memory.  If you have less than 
that (actually less than somewhat less than 4GB), nothing spills over to 
the normal zone.

>   Is it possible to have some of the
> guest's memory mapped in the Normal zone?

-m 8G

> Is there a good reference that talks about the normal, movable,
> etc. memory zones?

I expect Mel Gorman's book covers it.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.