5.1.1 Introduction

The first resource on a Windows NT server that is usually monitored is the CPU. CPUs have been gaining in power dramatically over the last few years and Windows NT supports a number of different processor architectures that are also supported by SQL Server 6.5. These are Intel, DEC Alpha AXP, MIPS and PowerPC.

As well as investing in the increasing power of a single processor system, more and more companies are purchasing Symmetric Multiprocessor (SMP) systems. Although a multiprocessor system may not reduce CPU bottlenecks when a single threaded process is consuming the CPU, multi-threaded processes such as SQL Server will benefit greatly.

CPU is a system resource. The more CPU power available the better the system is likely to perform. Windows NT schedules CPU time to the threads of a process and, if more threads require CPU time than there is CPU time available, a queue of waiting threads will develop. Sometimes a processor bottleneck is actually masking another bottleneck such as memory so it is important to look at CPU usage in conjunction with other resource usage on the system. This chapter provides an overview of CPU usage and looks at how SQL Server makes use of the CPU. It then looks at how CPU bottlenecks can be observed.

5.1.2 An Overview of Windows NT and CPU Utilization

To understand the way that Windows NT uses the CPU we first need to consider the difference between a process and a...