CPU hotplug

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Using the Linux cpuplugd Daemon to manage CPU and memory resources from z/VM Linux guests

Sizing Linux z/VM guests can be a challenging task. Oversized guests often cause additional management effort by the Hypervisor and undersized guests often have performance-related issues with workload peaks. A large amount of guests with large ratios of resource overcommitment (more virtual resources than are physically available) and changing workload characteristics over time makes a correct sizing even more challenging.

To simplify guest management the question is, why not let the system manage the resources automatically, based on the operating requirements of the guest. The Linux cpuplugd daemon, also called hotplug daemon, can control the amount of CPUs and memory available for a guest by adding or removing these resources according to predefined rules.

There is an updated version of the cpuplugd daemon available starting with SUSE Linux Enterprise Server (SLES) SP2 or Red Hat Enterprise Linux (RHEL) 6.2, which greatly enhances the capability to define rules and the available performance parameters for the rule set. This tool now provides exactly what is required to enable the operating system of the guest to manage the resources within the range of the guest definition.

This study analyzes various rules for the Linux cpuplugd daemon, which can be used to automatically adjust CPU and memory resources of a Linux z/VM guest.

Creation date
June 2012

CPU hotplug

The CPU hotplug function changes the number of used processors dynamically, depending on the current overall utilization and load.

The presentation covers the topics:

  • Functionality of CPU hotplug
  • How to enable CPU hotplug
  • Configuration recommendations
  • Examples for performance enhancements with CPU hotplug
Creation date
March 2009