What is a resource manager ?
While TORQUE has a built-in scheduler, pbs_sched, it is typically used solely as a resource manager with a scheduler making requests to it. Resources managers provide the low-level functionality to start, hold, cancel, and monitor jobs. Without these capabilities, a scheduler alone can not control jobs.
A resource manager is a daemon process that provides the interface between RMC and actual physical or logical entities. It is important to understand that although RMC provides the basic abstractions (resource classes, resources, and attributes) for representing physical or logical entities, it does not itself represent any actual entities. A resource manager maps actual entities to RMC’s abstractions. Each resource manager represents a specific set of administrative tasks or system features. The resource manager identifies the key physical or logical entity types related to that set of administrative tasks or system features, and defines resource classes to represent those entity types.
Since QNX Neutrino is a distributed, microkernel OS with virtually all nonkernel functionality provided by user-installable programs, a clean and well-defined interface is required between client programs and resource managers. All resource manager functions are documented; there’s no “magic” or private interface between the kernel and a resource manager. In fact, a resource manager is basically a user-level server program that accepts messages from other programs and, optionally, communicates with hardware. Again, the power and flexibility of our native IPC services allow the resource manager to be decoupled from the OS. The binding between the resource manager and the client programs that use the associated resource is done through a flexible mechanism called pathname space mapping. In pathname space mapping, an association is made between a pathname and a resource manager. The resource manager sets up this pathname space mapping by informing the process manager that it is the one re
In this chapter, we’ll take a look at what you need to understand in order to write a resource manager. A resource manager is simply a program with some well-defined characteristics. This program is called different things on different operating systems — some call them “device drivers,” “I/O managers,” “filesystems,” “drivers,” “devices,” and so on. In all cases, however, the goal of this program (which we’ll just call a resource manager) is to present an abstract view of some service. Also, since Neutrino is a POSIX-conforming operating system, it turns out that the abstraction is based on the POSIX specification.
