July 4, 2012

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

CPU and memory resources are normally shared in a virtualized environment. Therefore multiple guests are fighting for the same resources. Before the release of SLES11 SP2 and RHEL6.2 the automatic management of the number of virtual CPUs and the memory used in a virtual guest has been quite limited. Each system was requiring special attention and tuning of cpuplugd, the daemon that does the autonomic management in Linux on System z. Even then it had to be disabled for many systems.
The newer releases have a vastly improved daemon, that now allows for more detailed rules for adding and removing CPUs and memory to a guest. The drawback of more tuning knobs are more tuning knobs.
So this whitepaper tries to develop a recommended set of parameters to get the most benefit with the least effort. Furthermore results of measurements and experiments are shown together with the used parameters for advanced tuning.
Be aware that if you want cpuplugd to control memory and you run with more than one virtual CPU, you really want the fix for APAR VM65060 installed.
Also there has been a bug discovered in the base of SLES11 and RHEL 6 that's been fixed with maintweb kernel 3.0.42-0.7.3 for SLES 11 and the base RHEL 6.4 for Red Hat.

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