HP-UX Virtual Partitions Administrator Guide (includes A.05.08) (5900-1312, March 2011)

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.
CPU: Adding and Removing Bound CPUs
CPU Allocation Syntax In Brief
To understand how to assign CPUs, you need to understand the command syntax. Below is a brief
explanation of the CPU allocation syntax for the vparcreate command. For complete information,
see the vparcreate(1M), vparmodify(1M), and vparresources(5) manpages.
Syntax for vparcreate
The core vparcreate syntax for CPU allocation includes:
vparcreate -p partition_name [-a cpu::total] [-a cpu:::[min][:[max]]]
[[-a cpu:hw_path]...]
where:
• min is the number of CPUs bound to partition_name. The default is 1.
• total is the total number of bound plus unbound CPUs assigned to partition_name. The
default is 1.
• max is the maximum number of bound plus unbound CPUs that potentially can be added to
the partition. The default is the number of CPUs in the server.
3
3. When the vPars Monitor is running and you are not specifying an alternate database. If the vPars Monitor is not running
or you are specifying an alternate database, the max may be a different number.
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