HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM controls resources
Chapter 2 37
the maximum amount of CPU resources available to the PRM group is
based on the number of cores assigned to the group. You can assign a
maximum amount of memory to a PSET PRM group. These maximum
amounts, known as caps, are not available for disk bandwidth for either
type of PRM group. Shared memory allocations are static in size, so no
caps are needed.
How shares work
A share is a guaranteed minimum when the system is at peak load.
When the system is not at peak load, PRM shares are not
enforced—unless CPUCAPON mode is enabled, in which case CPU shares
are always enforced.
Valid values for shares are integers from one to MAXINT (the maximum
integer value allowed for the system). PRM calculates the sum of the
shares, then allocates a percentage of the system resource to each PRM
group based on its shares relative to the sum.
Table 2-2 shows how shares determine CPU resource percentage. The
total number of shares assigned is four. Divide each group’s number of
shares by four to find that group’s CPU resource percentage. This CPU
resource percentage applies only to those cores available to FSS PRM
groups. If PSET PRM groups are configured, the cores assigned to them
are no longer available to the FSS PRM groups. In such a case, the CPU
resource percentage would be based on a reduced number of cores.
Shares allow you to add or remove a PRM group to a configuration, or
alter the distribution of resources in an existing configuration,
concentrating only on the relative proportion of resources and not the
total sum. For example, assume we add another group to our
configuration in Table 2-2, giving us the new configuration in Table 2-3.
Table 2-2 Converting shares to percentages
PRM group CPU shares CPU resource %
GroupA 1 1/4 = 25.00%
GroupB 2 2/4 = 50.00%
OTHERS 1 1/4 = 25.00%