Beth A. Glendening

Logical partition mode physical resource management on the IBM eServer z990

The IBM eServerTM z990 provides tremendously increased processor, I/O, and memory capacity exceeding the capability of even the premier IBM operating systems. The modular or book-form system topology of the z990 enables a highly flexible and more cost-effective concurrent upgrade infrastructure, as well as improved hardware failure survivability and serviceability. The multibook form of the z990 has two significant memory access performance issues which are addressed here: First, there is increased cache coherency overhead when the same memory is accessed by central processing units (CPUs) from multiple books; second, access from CPUs to memory on books other than the book on which a CPU is resident is not as efficient as access from the same book. Awareness of this multifold increase in capacity and complexity is effectively managed by the IBM zSeries® logical partition (LPAR) hypervisor, obviating the need for operating system involvement. This paper describes changes made to the zSeries LPAR hypervisor to manage CPU and memory resources on the z990 machine topology.