To check how many free resources (in terms of memory and VCPUs) there are on the compute nodes, you can use the script free_resources_compute_nodes.sh installed on cld-ctrl-01.
You can check a single compute node, e.g:
/usr/local/bin/free_resources_compute_nodes.sh cld-np-03.cloud.pd.infn.it
or all hypervisors:
/usr/local/bin/free_resources_compute_nodes.sh all