Abstract

Successful consolidation of multiple workloads on to a single server demands that users be guaranteed consistent levels of workload performance. Users should be able to define Service Level Objectives (SLO), specifying the performance goals they seek and their relative importance. To achieve target performance consistently, applications' access to resources such as CPU and memory must be adjusted automatically. Workload managers can be classified in to two categories. An entitlement-based manager allocates resources based on a specification of resource entitlements. Goal-based workload managers adjust the resources allocated to a workload, based on a specification of performance goals. Entitlement-based and goal-based workload managers have been supported in some commercial and experimental systems. Several UNIX OS vendors implement entitlement-based resource managers, which do not use any feed-back mechanism to meet performance goals. IBM's OS/390 goal-based workload manager (WLM) employs extensive instrumentation to gather detailed information about an appli-cation's resource needs, and adjusts resource allocations. Adjusting the use of system resources to meet response time goals has been in wide use in Transaction Processing (TP). Several experimental transaction processing sys-tems have exploited feedback mechanisms to meet response time goals.

The HP-UX Workload Manager is distinct from the sys-tems discussed above that also use feedback control to adjust resources. First, the workload manager does not monitor workload performance directly. Instead, it receives a work-load's performance data through an API from a performance monitor created by the application provider (or system administrator). Second, the workload manager uses a simple proportional controller to determine the resources that must be allocated to a workload. Third, the workload manager has been designed to take advantage of the existing infrastructure of tools that includes Process Resource Manager (PRM), and the Event Monitoring Service (EMS, which raises an alarm when a performance goal is not being met). Fourth, unlike TP monitors, which handle workload management exclusively for transaction processing systems, the HP-UX Workload Manager can handle a wide variety of application workloads.

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