Receivers and Donors

A receiver is the service class period SRM is considering helping. SRM helps only one receiver during each policy interval, although it may assess multiple receivers before finding one to help. A donor is a service class period that donates resources to the receiver. Multiple donors may donate multiple resources to a single receiver during one policy interval.

The resources to help the receiver may also come out of what is referred to as discretionary resources. Discretionary resources are those that can be reallocated with little or no effect on the system's ability to meet performance goals.

Service class periods other than receivers and donors can also be affected by changes. These service class periods are referred to as secondary receivers and donors. SRM may decide not to help a receiver due to minimal net value for either a primary or secondary donor. Action Trace Example explains an example in which there are secondary receivers and donors.

If a service class period is being served by one or more address spaces, it is called the goal receiver or donor. It is the service class period with the response time goals. To help such service class periods, SRM must donate resources to the server address spaces. The service class period serving a service class, is called a resource receiver or donor. SRM adjusts resources for the resource receiver/donor to affect the performance of the goal receiver/donor.