Installation guide

5.3.6 Managing Subsystem Attributes
Occasionally, to improve the performance of a subsystem or of the system
as a whole, you might modify the value of subsystem attributes. You use
the /sbin/sysconfig command to determine the names and values of
subsystem attributes. You can also use the command to modify the value of
a small number of attributes in the currently running kernel.
If you modify an attribute at run time by using the /sbin/sysconfig
command, the modification persists as long as the system is running. If you
shut down and reboot the system, the modification is lost. To modify
subsystem attributes so that changes persist across reboots, store the
attribute’s value in the /etc/sysconfigtab database, as described in
Section 5.3.8.
The system parameters that are set in the system configuration file and in
the param.c file continue to define the system tables, and should be
viewed as establishing default values in the kernel. You can override these
values by using the /sbin/sysconfig command or by storing a value in
the /etc/sysconfigtab database. For more information about the
configuration file and param.c, see Section 5.4.
You can manage dynamic subsystem attributes either locally or remotely.
For information on how to use the /sbin/sysconfig command remotely,
see Section 5.3.7.
5.3.6.1 Determining the Value of Subsystem Attributes
Use the /sbin/sysconfig -q command to determine the value assigned
to subsystem attributes. When you issue the /sbin/sysconfig -q
command the subsystem you specify on the command line must be loaded
and configured. For information about getting a list of the loaded and
configured subsystems, see Section 5.3.2.
The following example shows how to use this command to determine which
attributes are part of the generic subsystem:
# /sbin/sysconfig -q generic
generic:
clock-frequency = 1024
booted_kernel = vmunix
booted_args = vmunix modules=0xfffffc00005ea000
lockmode = 0
lockdebug = 0
locktimeout = 15
max-lock-per-thread = 8
lockmaxcycles = 0
rt_preempt_opt = 0
5–10 Configuring the Kernel