If Y, mbatchd reserves resources based on job slots instead of per-host.
bsub -n 4 -R "rusage[mem=500]" -q reservation my_job
requires the job to reserve 500 MB on each host where the job runs.
Some parallel jobs need to reserve resources based on job slots, rather than by host. In this example, if per-slot reservation is enabled by RESOURCE_RESERVE_PER_SLOT, the job my_job must reserve 500 MB of memory for each job slot (4*500=2 GB) on the host in order to run.