[pve-devel] some finding avout minimum static memory when pc-dimm exists

Alexandre DERUMIER aderumier at odiso.com
Fri Jan 23 17:42:59 CET 2015


I have done some tests,

and it's seem that the minimum memory when pc-dimm exists, is 512MB

(I have read some discussion mailing about pci hole, but I don't understand all the things ;).

On a linux machine booting fine with -m 128 , it don't work with -m 128 -pcdimm 1024 ... for example.

-m 510 -pcdimm 1024 don't boot 

-m 512 -pcdimm 1024 boot

(linux hang on initramfs, and windows on kernel loading)

I need to do some tests with numa, multi cores to see exactly what is the minimum value.

But maybe could be do something like:

without dimm hotplug
memory: 1024

kvm -m 1024

with dimm hotplug
memory: 1024
maxmemory: 8192  (this enable dimm hotplug)

kvm -m size=512,slots=255,maxmemory=8192  -pcdimm 512M ....

We reserve the first 512M as static, and assign pcdimms for the remaining memory.

Like this we only need 1 memory option (min:512), which seem easier for user.

What do you think about it ?

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