SRIOV performance vs number of VFs configured


Recently I got information that number of configure VFs impacts performance.

Specifically the situation was as follows.For simplicity reasons we are usually configuring max available VFs (63). But recently I was told (by people concerned with VNFs deployment) that due to performance reasons we should configure only the number of VFs that are actually use by VNF. Unfortunately I was not presented with any data (or documentation) to support their claim.

I would be grateful for any data or pointing my to any documentation that supports (or disproves) the claim about performance impact.

Thanks in advance,