1. In a computer system employing system virtualization partitioning in which each of multiple logical partitions operates in a logically independent manner from other partitions using shared physical resources of the computer system, a method for balancing access among the multiple logical partitions to the physical system resources, said method comprising: utilizing hardware detection logic to collect performance metrics of one or more of the physical system resources in association with one or more of the logical partitions; classifying each of the logical partitions in accordance with a level of allocated dispatch window utilization; and during a dispatch window in which a given set of the physical system resources are pre-configured for allocation to one of the logical partitions, allocating the given set of physical system resources to a replacement logical partition in accordance with the collected performance metrics associated with the replacement logical partition and the dispatch window utilization classification of the replacement logical partition.