Re: [PATCH 2 of 4 v7/leftover] libxl: enable automatic placement of guests on NUMA nodes

[Andre Przywara <andre.przywara@amd.com>]

On 07/24/2012 04:42 PM, Dario Faggioli wrote:
> If a domain does not have a VCPU affinity, try to pin it automatically
> to some PCPUs. This is done taking into account the NUMA characteristics
> of the host. In fact, we look for a combination of host's NUMA nodes
> with enough free memory and number of PCPUs for the new domain, and pin
> it to the VCPUs of those nodes.

I have tested this version 7 on my box in various configurations:
1. Homogeneous memory distribution: 8 nodes, each 16 GB
2. "Odd" configuration: 8 nodes, 4 have 8 GB, 4 have 16 GB
3  Flat memory (by using cpus="all")

I created up to 32 guests with 2 VCPUs and 2 GB each and observed the 
distribution after every 8th guest.
Another round with 2 VCPU guests, but this time with memory sizes 
varying from 512MB to 5120MB.

The placement was running well in all cases.
The only thing I saw as a little sub-optimal placement in the odd 
configuration (2) with the differently sized guests. This is probably a 
side effect of Dom0 ballooning, which is not really NUMA aware AFAIK. 
This leads to a situation, where some nodes just by chance have less 
memory than a certain guest needs and so are not considered candidates.
I think we can perfectly tolerate this behavior for now. I didn't see 
anything strange with config 1.

So this patch gets my:

Tested-by: Andre Przywara <andre.przywara@amd.com>

Please apply to 4.2-unstable!

Regards,
Andre.