idtune(ADM)

idtune -- set or get the value of a tunable parameter

Synopsis

/etc/conf/bin/idtune [-f | -m] [-c] parm value
/etc/conf/bin/idtune -g [-c] parm
/etc/conf/bin/idtune -d [-c] parm

Description

One of the ID/TP kernel configuration tools, idtune sets or gets the value of an existing tunable parameter. idtune is called by a Driver Software Package (DSP) installation or removal script; it can also be invoked directly as a user-level command. New tunable parameters must be installed using idinstall(ADM) and a DSP Mtune file before they can be accessed using idtune.

Note that existing tunable parameter values must be modified using the idtune command.

There are three different ways to use the idtune command, which are explained in the ``Usage'' section.

Options

-f

Force the change of the tunable parameter parm to value and suppress all confirmation messages. If the -c option is used with the -f option, the values in both stune.current and stune are changed; otherwise, only the tunable parameter value in stune is changed. This option does not apply to string tunables.

-m

Change the value of parm, but only if the existing value is smaller than the value specified by this idtune command. If the -c option is used with the -m option, the values in both stune.current and stune are changed; otherwise, only the tunable parameter value in stune is changed.

-c

Apply the change to the tunable parameter in both stune and stune.current. Note that all changes made to stune.current will affect any loadable kernel modules configured thereafter, and can potentially create inconsistencies between the running kernel and the new loadable kernel modules. For this reason, the -c option should be used with caution.

-g

Print the following sequence of values (separated by white space) to stdout:

the current value of the tunable parameter
the default value, from the Mtune entry
the minimum valid value, from the Mtune entry
the maximum valid value, from the Mtune entry

Only the first two values apply to string tunables. For tunables that are autotuned by default and have not had this autotuning overridden with a specific value using idtune, the values shown are for the present amount of memory. If they have been overridden, the default, minimum, and maximum are for the present amount of memory, and the current is the specified value.

If the -c option is used with the -g option, the current value in the kernel currently running is displayed; otherwise, the value that will be used in the next system build is displayed.

-d parm

Reset the tunable parameter to its default value. If the tunable is autotuned by default, resets it to autotuning. If the -c option is used with the -d option, the values in both stune.current and stune are reset; otherwise, only the tunable parameter value in stune is reset. All confirmation messages are suppressed.

Usage

The first form of the idtune command, with no options or with -f or -m, is used to change the value of a parameter. The tunable parameter to be changed is indicated by parm, and the desired value for the tunable parameter is value.

By default, if the parameter in the stune file has a value, you are prompted to confirm the change with the following message:

   Tunable Parameter parm is currently set to old_value in
     /etc/conf/cf.d/stune
   Is it OK to change it to value? (y/n)

If the parameter is autotuned by default, you are prompted to confirm the change (which will override autotuning) with the message:

   Tunable Parameter parm is currently autotuned.
   Is it OK to change it to value? (y/n)

For either of these questions, if you answer y, the change is made. Otherwise, the tunable parameter will not be changed, and the following message is displayed:

   parm left at old_value

However, if you use the -f (force) option, the change is always made and no messages are reported.

If you use the -m (minimum) option, and there is an existing value which is greater than the desired value, no change is made and no messages are reported. This option only applies to integer tunables.

If you use the -c (current) option with the first form of the idtune command, the change applies to both stune and stune.current; otherwise, only the tunable parameter in stune is affected. Because any change made to the stune.current file will affect all the loadable kernel modules configured thereafter, it is very easy to introduce inconsistencies between the currently running kernel and the new loadable kernel modules. Therefore, you should be extremely careful when using the -c option.

If you are modifying system tunable parameters as part of a device driver or application add-on package, you might want to change parameter values without prompting Your add-on package Install script could override the existing value using the -f or -m options. However, you must be careful not to invalidate a tunable parameter modified earlier by the user or another add-on package.

Any attempt to set a parameter to a value outside the valid minimum/maximum (as given in the Mtune file) range will be reported as an error, even when using the -f or -m options. No validation is performed for string tunables.

The UNIX^® system kernel must be rebuilt (using idbuild(ADM)) and the system rebooted for any changes to tunable parameter values in stune to take effect.

Exit codes

The exit status will be non-zero if errors are encountered.

References

idbuild(ADM), idinstall(ADM), Mtune(DSP), stune(DSP)