HP Process Resource Manager (PRM) Standard HP-UX resource allocation, Resources managed by PRM

Table 1 Resources managed by PRM

Resource managed	Shares	Cap
CPU	Yes (for FSS PRM	Yes[LINEBREAK](on
	groups)	all groups in
		CPUCAPON mode;

on a per-group basis is also available for HP-UX 11i v3 and later)

Management algorithm

PRM allocates time slices to FSS PRM groups proportional to their shares. When CPUCAPON mode is enabled, the FSS PRM group is given CPU time regardless of whether the time is needed. With per-group capping, the CPU time remains available to other PRM groups.

For PSET PRM groups, PRM allocates entire cores to the group according to the current configuration. CPU capping for PSET PRM groups is a result of the number of cores assigned to the group.

Real memory (private)	Yes	Yes	When the system is paging (real memory is
		[LINEBREAK](on a exhausted), if a PRM group is exceeding its
		per-group basis)	shares, the Memory Resource Groups (MRG)
			kernel causes the process to page.
Real memory (shared)	N/A	N/A	The amount of memory requested is set aside for
			use as shared memory.

Standard HP-UX resource allocation

Under standard HP-UX resource allocation, all processes are treated equally. Figure 1 illustrates how a user, by starting multiple processes, can consume a majority of an available resource because the processes each get equal amounts. As illustrated, User1 starts two processes and User2 starts one process. Using HP-UX standard resource allocation, User1 could control two-thirds of the available resource while User2 gets one-third, regardless of the importance of each process.

Figure 1 HP-UX standard resource allocation

	PROCESS1
		33.3%
	PROCESS2
		33.3%		33.3%	PROCESS3
USER1
			HP-UX SERVER

USER2

How PRM can improve on standard allocation

Unlike the standard scheduler, PRM allows you to set priorities on your processes. The following sections illustrate various ways you can use PRM to improve scheduling.

If multiple users or applications within a PRM group are competing for resources, standard HP-UX resource management practices determine resource allocation.

Balancing resource use between users

Figure 2 shows how PRM can alter standard resource allocation and balance system resource use.

In the following scenario, a service provider wants each customer to have an equal share of the machine. Each customer is assigned to a separate PRM group, which is given resource shares equivalent to 50%. The resource being allocated could be either CPU or memory. This configuration guarantees each PRM group 50% of the resource for any given interval. Thus, Customer2’s process receives 50% of the resource; however, because Customer1’s group contains two processes, each

14 Overview