Autotuned parameters
Autotuned parameters are kernel variables whose default
values are automatically tuned according to the amount
of memory that the system has.
For large memory systems (those with more than 1GB of
general purpose memory) a distinction is made
between autouned parameters which consume kernel virtual
memory and those that simply manage physical memory.
-
Parameters related to virtual memory are calculated according
to the amount of general purpose memory (memory that is managed by page
tables, not dedicated memory) present on the system.
These parameters are defined by a line in the
Autotune(DSP),
file, where the first field is the
parameter name, and the second field is ``PHYS''.
In this documentation, these parameters are identified in tables
by ``PHYS'' in the ``Auto'' column.
-
Parameters that are used for calculations that consume kernel virtual memory
are also calculated according to the amount of general purpose memory
available, but on systems that have greater than 1GB of memory, these
parameters are limited by the amount of kernel virtual memory available.
If there is no ``PHYS'' entry for a parameter in the
Autotune(DSP)
file, the autotune value is calculated using this method.
In this documentation, these parameters are identified in tables
by ``KVM'' in the ``Auto'' column.
For autotuned parameters, a table of information
is provided from which mtune entries are created.
This table is passed to the kernel to allow autotuning of these
parameters when the system is initialized.
The mtune lines are recalculated whenever idtune
or idbuild is run.
The command idtune -g tunable-name provides the
current, default, minimum, and maximum information for the
tunable based on the amount of memory currently available.
The files specifying default, minimum and maximum values
are in /etc/conf/autotune.d.
The format for a line in an autotune file is:
``tunable-name'' ``record-type'' ``LINEAR|STEP'' ``memsize (in MB)'' ``value''
The fields are:
``tunable-name''-
The name of the tunable parameter.
``record-type''-
A ``PHYS'' entry in this field indicates that the parameter is
autotuned using a method based on the amount of general purpose memory
available.
If the ``record type'' is ``PHYS'', subsequent fields are not used.
Otherwise, the parameter is autotuned using a (default) method that
takes both general purpose and kernel virtual memory into account.
In this case, information is provided about whether the line pertains to the
default value (``DEF''), minimum value (``MIN''),
or maximum value (``MAX'').
``LINEAR | STEP''-
Indicates whether values for larger amounts of memory should be calculated
linearly or as a step function
If the entry in the ``record type'' field is ``PHYS''
this field is not used.
``memsize''-
The number of megabytes this line specifies information about.
If the entry in the ``record type'' field is ``PHYS''
this field is not used.
``value''-
The value of the parameter for the specified amount of memory.
If the entry in the ``record type'' field is ``PHYS''
this field is not used.
Do not edit these files directly; instead, use
configure(ADM)
or
idtune(ADM).
If you add memory after tuning one of these tunables, perform an
idtune -d tunable_name to reset autotuning.
For some parameters, the default and maximum values are autotuned;
for others, only the maximum value is autotuned.
Next topic:
Special case tuning needs
Previous topic:
About tunable parameters
© 2007 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 05 June 2007