The VM/370 Resource Limiter
David M. Chess, G. Waldbaum · IBM Systems Journal · 1981
RESLIM has proved to be a useful workload management tool for users, user management, and computing center personnel. On a daily basis, RESLIM discovers about ten undesired program loops and automatically reduces the performance impact of these loops by degrading the offending virtual machine's priority. This saves hours of processing time yet preserves the faulty state of the users' virtual machines to facilitate on-line debugging. The most notable feature of RESLIM is its unique position in the resource allocation hierarchy. It is more specific in function and more easily modified than the VM scheduler and yet makes possible a degree of automation that can free management from the responsibility of directly watching over the system andta king action manually. While it is likely that certain of RESLIM'S functions could be performed by a sufficiently sophisticated scheduler, it is also clear that the ease with which management can alter its functional parameters stems directly from its implementation as a separate virtual machine. And in an environment which is heavily resource-constrained, the ability to make prompt, specific changes in the allocation and control of those resources can be a great advantage.