HP-UX Virtual Partitions Administrator's Guide (includes A.03.05 and A.04.05)

CPU: Bound and Unbound
Definitions
With vPars, there are two types of CPUs: bound and unbound.
A bound CPU is a CPU that is assigned to and handles I/O interrupts for a virtual partition. Every
virtual partition must have at least one bound CPU to handle its I/O interrupts.
CPUs that are not assigned to any virtual partition or that are assigned to a virtual partition but
do not handle its I/O interrupts are unbound CPUs. Unbound CPUs are sometimes called floater
CPUs.
All CPUs begin as not being assigned to any virtual partition, so all CPUs begin as unbound
CPUs. Using the vPars commands, you can assign CPUs to virtual partitions as bound or unbound.
You can migrate both bound and unbound CPUs, but because HP-UX cannot dynamically migrate
I/O interrupts, you can dynamically migrate only unbound CPUs.
CPU: Determining Whether to Use Bound or Unbound
When the applications within the target virtual partitions are I/O intensive, use bound CPUs
because only bound CPUs can process I/O interrupts; specifically, with I/O intensive applications
there should be more bound CPUs than unbound CPUs.
If your applications are CPU intensive (and not I/O intensive), use unbound CPUs so that you
can easily adjust the number of CPUs via dynamic CPU migration as the demand on the virtual
partition changes. Unbound CPUs provide greater flexibility of movement between virtual
partitions because they can be added and removed without needing to bring down the affected
partitions.
CPU: Determining When to Specify a Hardware Path for a Bound CPU
By default, the vPars Monitor chooses the hardware path of a bound CPU. However, if you need
to use a specific CPU, you can specify its hardware path in the vPars commands.
Generally, you do not need to specify a hardware path. The main purpose of specifying hardware
paths is when you need to consider NUMA (Non-Uniform Memory Access) factors, where the
distance between a CPU and memory is critical to performance.
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