intctl.1m (2010 09)

i
intctl(1M) intctl(1M)
interrupts to be assigned to a smaller set of CPUs causing an imbalance and thus a non-optimally
configured system.
Using the
-b option allows the user to manually balance the interrupt distribution of the system. Users
can choose one of these two balancing algorithms to balance interrupts:
• driver_weight
The default balancing algorithm used by
intctl is
driver_weight. This balancing algorithm
associates weights to each driver based on its interrupt frequency. The system is balanced such that
each CPU is loaded with a similar average weight from the interrupt load perspective.
• round_robin
The
round_robin balancing algorithm assigns interrupts to the available CPUs in a rotating round
robin fashion. The round robin assignment is similar to the HP-UX default boot time interrupt distri-
bution method. However, the interrupt assignments can differ because of the different ways that I/O
cards and CPUs are discovered.
driver_weight
is a better choice of algorithm for systems having I/O cards that demand largely vary-
ing range of interrupt processing needs. Hence,
driver_weight is the default algorithm.
In systems where all I/O cards demand similar interrupt processing capacity or when there is difficulty
determining interrupt load generated by each driver, then the
round_robin algorithm can be used.
Administrators can also configure automatic balancing of interrupts at periodic intervals. Balancing is
performed only if there is an interrupt distribution imbalance. This kind of interrupt balancing is desir-
able in a dynamic CPU migration environment such as WLM (Work load Manager). Refer to
intrbald (1M) for more details.
Several settings are provided for managing balancing of interrupts. These settings are to be provided
using the
intctl command line options or can be persistently configured in the /etc/intctl.conf
configuration file. See the Interrupt Configuration File section below.
Options
By default, the
intctl command displays interrupt information about all the interface cards on the sys-
tem.
intctl recognizes the following options:
-a algorithm Balancing of interrupts can be performed any time during system up time to reduce CPU
overload because of interrupt handling.
The algorithm parameter specifies which of the following interrupt balancing algorithms
to use:
•
driver_weight (-a driver_weight
). This balancing algorithm is also the
default algorithm. The default can also be set by changing
INTCTL_DEFAULT_ALGO
in the /etc/intctl.conf
configuration file to driver_weight. Refer to the
Interrupt Configuration File section of this manpage for more information.
Each driver is given a weight based on the number of interrupts it can generate.
Balancing operations ensure that each CPU is loaded (from interrupt load perspec-
tive) with a comparable total driver weight. These weights can be between
0 and
INT_MAX (see limits (5)). Most of the HP-UX drivers are already defined in the
configuration file section, INTCTL_DRIVER_WEIGHTS. Users can modify or over-
ride these driver weights, but they should make sure not to set unrealistic driver
weights without knowing the amount of interrupt load the driver could generate.
• round_robin (
-a round_robin).
Each interrupt in the system is assigned an available CPU in round robin fashion.
This balancing approach can be used when it becomes difficult to differentiate drivers
based on their interrupt load. Compared to the driver weight based approach, round
robin could result in more interrupt migrations while balancing interrupts.
-b Balance the interrupt distribution of the system by performing the least number of
migrations that can distribute interrupt load across a specified set of CPUs.
Options
-a, -i, -o are provided to be (optionally) used in conjunction with the -b
option. These options are basically provided to improve the control and flexibility of the
user while balancing interrupts. See the description for the -a, -i, -o options.
2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010