mtune(4)                                                              mtune(4)


NAME
     mtune - default system tunable parameters

DESCRIPTION
     The directory /var/sysgen/mtune contains information about all the system
     tunable parameters, including default values.  The files in this
     directory should never be changed.  Instead, use the systune(1M) utility
     to change parameters in the /var/sysgen/stune file.

     Each loadable module can have its own mtune file, which is placed in the
     mtune directory and has the same name as the module.  Parameters in an
     mtune file may be grouped together in groups, according to the nature of
     the parameters.  For example, all parameters dealing with the number of
     processes that can run on the system at any given time are grouped
     together in the numproc group in the kernel module.  The syntax of an
     mtune module file is given below:

          [group_name: [flag]]
          parameter_clauses

     Names that end with a colon character, :, are group names.  Parameters
     can be grouped together in groups so that one sanity checking function
     can be used to verify the values and the dependencies between these
     variables.  The group name is optional if there is only one group in the
     module.  For this case, the configuration tools use the module name as
     the group name.

     The group name is followed by a flag.  The flag can be either run or
     static.  If the flag is run, this group of tunable variables can be
     changed with the command systune on a running system.  Otherwise, the
     variables are set at initialization time and can be changed only by
     creating a new kernel and booting that kernel.  Modules with no group
     specifier or a group specifier without a flag default to static.

     Each tunable parameter is specified by a single line, a parameter clause,
     in the file.  Blank lines and lines beginning with # or * are considered
     comments and are ignored.  The syntax for each line is:

          name[,tag] default_value [[min_value [max_value [ll|LL]]

     name             The name of the tunable parameter.  It is used to pass
                      the value to the system when a kernel is built or
                      changed by systune command.  Since this name is made
                      into a global variable name, using a long descriptive
                      name is useful to avoid any name collisions.

     tag              This optional field is separated from name by a comma.
                      It is used to qualify whether the tunable parameter
                      should be used in the configuration being built.  This
                      allows a single tune file to be used in multiple
                      different configurations.  Parameters without any tag
                      are always used, those with a tag are only used if the


                      tag matches one of the tags specified in the system file
                      (see system(4)).  Only one tag is permitted on a given
                      line.

     default_value    The default value of the tunable parameter.  If the
                      value is not specified in the stune file, this value is
                      used when the system is built.  This value is mandatory.

     min_value        The minimum allowable value for the tunable parameter.
                      If the parameter is set in the stune file, the lboot
                      command checks that the new value is equal to or greater
                      than this value.  The command systune also verifies the
                      new value against this value before changing the system.
                      This field is optional; not specifying a value is
                      equivalent to specifying a zero value.  Except in the
                      case where max_value is non-zero, a value of zero for
                      min_value excludes range checks from being performed
                      against min_value.

     max_value        The maximum allowable value for the tunable parameter.
                      If the parameter is set in the stune file, the lboot
                      command checks that the new value is equal to or less
                      than this value.  The command systune also verifies the
                      new value against this value before changing the system.
                      This field is optional; not specifying a value is
                      equivalent to specifying a zero value.  A value of zero
                      for max_value excludes range checks from being performed
                      against max_value.

     ll|LL            By default, each tunable parameter is represented by an
                      global variable in the kernel of type int (32 bits).
                      Some tunable parameters may need to be specified as 64
                      bit quantities.  Adding an ll or LL to the end of the
                      parameter specification causes lboot to represent the
                      parameter as a long long.

FILES
     /var/sysgen/mtune/*    default system tunable parameters
     /var/sysgen/stune      local settings for system tunable parameters
     /var/sysgen/system/*   master system configuration files

SEE ALSO
     lboot(1M), systune(1M), stune(4), system(4).


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