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

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@xxxxxxx>

Please apply to 4.2-unstable!


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