HP Process Resource Manager User's Guide

Configuring and enabling PRM on the command line
Configuring PRM
Chapter 7 105
You can explicitly add the PRM_SYS (PRMID 0) group to a configuration
file. However, if you explicitly add the PRM_SYS group to a configuration
file, it gets the CPU shares you assign it, which must equate to at least
20%.
You can also assign disk bandwidth shares to an explicitly defined
PRM_SYS group.
You cannot, however, assign memory shares to an explicitly defined
PRM_SYS group. Consequently, you also cannot specify memory shares for
any other group in a configuration where the PRM_SYS group is explicitly
defined due to the required one-to-one correspondence between
group/CPU records and memory records. The PRM_SYS group is allowed
to use as much memory as it needs.
If you do not explicitly add PRM_SYS to your configuration, it is created
automatically and appears in the output of prmmonitor -s and ps -P in
parentheses: (PRM_SYS).
By default, all processes run by root (user ID of 0) are placed in the
PRM_SYS group—unless the processes have application records or are
moved manually.
Do not consider the PRM_SYS group or its default shares when
determining resource shares. The shares you assign in a PRM
configuration file divide what remains after PRM_SYS is granted its
resources. Typically, PRM_SYS resource use is minimal.
When CPU capping is enabled, the PRM scheduler does not schedule
processes for the next PRM group until the current group’s CPU time has
elapsed. However, the PRM_SYS group is not required to use its entire
CPU time slice before the scheduler allocates time to the next PRM
group. In effect, this unused time is distributed to the other PRM groups
according to their relative number of their shares.
The PRMID 1 group, which is named OTHERS, is the default for users who
do not have assigned initial groups. You must explicitly define this group
in your configuration file, although you do not have to use the default
name.
Group/CPU record syntax
This section explains the syntax of group/CPU records.
Group/CPU records specify PRM groups and their CPU allocations in
your configuration file.