HP-UX Processor Sets

HP-UX Processor Sets 8
Scheduling Allocation Domain
A Scheduling Allocation Domain for an application defines which processors the application
may execute on in the system. Without processor sets, an application has access to all
processors in the system. Depending on the system workload scheduling policies and
priorities, the operating system scheduler may execute the application on any processor in the
system. We cannot isolate processor(s) for a given application. The entire system is the
Scheduling Allocation Domain for an application. As a result, all applications compete with
one another for processor cycles based on their scheduling policies and priorities.
(Note: If an
application chooses explicit processor affinity, then the scheduler executes the application
only on the processor chosen by the application)
.
HP-UX Processor Sets provide privileged users the ability to define and manage a Scheduling
Allocation Domain for an application. By grouping processors together for the exclusive use of
specific applications, HP-UX Processor Sets define individual Scheduling Allocation Domains,
thus preventing applications assigned to different processor sets from contending with one
another for processor resources.
HP-UX Processor Sets support multiple instances of the POSIX Real Time Scheduler — one
for every processor set. (Each POSIX Real Time Scheduler need to run on a global basis
within its particular Scheduling Allocation Domain.) Applications using the POSIX Real Time
scheduling policies in different processor sets do not contend with one another.
The HP-UX operating system load balancer works only
within a processor set. The system
does not implicitly perform any load balancing across processor sets. The user is responsible
for ensuring the proper processor set configuration and workload distribution among the
processor sets.
Configuring Processor Sets
When booted, the HP-UX system starts with one user-visible processor set — the Default
Pset — to which all enabled processors in the system are assigned. Users can then
dynamically create additional new processor sets. A newly created processor set has no
processors assigned to it. Every processor set is assigned a unique identifier (psetid) at
creation, and this identifier can be used to perform further operations on the processor set.
(Note: Users do not have explicit control over which psetid is assigned to a newly created
processor set).
All enabled processors in the system have a processor set assignment, but a processor can
only be assigned to just one user-defined processor set at a time. However, with the