kctune.1m (2010 09)

k
kctune(1M) kctune(1M)
Default State for Tunables
The default value for a tunable is not necessarily fixed. Default values can change between HP-UX
releases, or in patches. Some tunables have default values that are re-computed at boot time, or when
there is a change to the hardware configuration of the system. Some tunables change their default values
in response to changing system workloads. These tunables are called "Automatic" tunables and are
marked in kctune output.
When a tunable is set to
Default, its value is controlled by the HP-UX kernel, and will be changed
whenever the default value for the tunable is re-computed. Specific behavior of each tunable is described
in each tunable’s man page. HP recommends that all tunables be set to
Default unless the default
value is known to be unsatisfactory.
Setting a tunable to its default value is not the same as setting it to
Default. If the current default
value of a tunable
example is 4000,
kctune example=4000
will set the tunable’s value to 4000 and prevent it from changing when the default value is re-computed.
kctune example=Default
will set the tunable’s value to 4000, and automatically change it whenever the default value is re-
computed.
Developer’s Note
The layout and content of
kctune’s output may change without notice, except when -P fields is specified.
Scripts or applications that need to parse the output of
kctune are expected to use the
-P fields option.
See kconfig(5) for details.
The fields supported in a
kctune request are:
auto_default This field contains a y if the tunable’s default value is automatically computed by
the system (and can therefore change over time), or an n otherwise.
before The value that was in use for the tunable before the change that was just made, if
known. For saved configurations, the previous value of some tunables may not be
known. If the value was specified using an expression, this field contains the
result of evaluating that expression. This field is present only for tunables for
which an immediate value change has been made during the current invocation of
kctune.
before_default This field contains a
y if the tunable was set to its default value before this invo-
cation of
kctune,orann otherwise. This field is present only for tunables for
which an immediate value change has been made during the current invocation of
kctune.
before_expr The expression for the tunable’s value before the change that was just made, if
any. If the tunable was set to default, this field contains the word Default.
This field is present only for tunables for which an immediate value change has
been made during the current invocation of kctune.
bootvalue The value of the tunable at the time the system last booted. This field is not
printed for saved configurations.
canauto This field contains a y if the tunable is capable of being automatically tuned, or
an n otherwise.
constraint This field contains the constraints between this tunable and others. There may
be zero or more values of this field for any tunable.
current The current value of the tunable, if known. For saved configurations, the current
value of some tunables may not be known until the configuration is in use. If the
value was specified using an expression, this field contains the result of evaluat-
ing that expression. If the tunable is being automatically tuned, this field con-
tains the value the kernel is currently using.
desc A short description of the tunable.
default This field contains a y if the tunable is set to its default value, or an n otherwise.
If all three of default, auto_default, and canauto are y, the tunable is
being automatically tuned.
HP-UX 11i Version 3: September 2010 − 3 − Hewlett-Packard Company 3