Managing CPU-Intensive Work on Uniprocessor LPARs

Overview

Uniprocessor systems may exist as either an LPAR on a single-engine physical processor or as a "Small LPAR" on a larger n-way physical processor. For this discussion, a "Small LPAR" is one that is guaranteed less than 50% of an engine based on its assigned weight when the processor runs at capacity. Often, a minimum of two logical CPs will be assigned to these small LPARs because clients are concerned about uniprocessor systems. However, running a small LPAR as a 2-way can result in "Short engines" and cause performance problems. "Short engines" occur on busy processors when the number of logical CPs exceeds the number guaranteed to an LPAR based on its weight.