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File Formats                                          ts_dptbl(4)



NAME
     ts_dptbl - time-sharing dispatcher parameter table

DESCRIPTION
     The process scheduler (or dispatcher) is the portion of  the
     kernel that controls allocation of the CPU to processes. The
     scheduler supports the notion of  scheduling  classes  where
     each  class  defines  a  scheduling policy, used to schedule
     processes within that class. Associated with each scheduling
     class  is  a  set  of  priority queues on which ready to run
     processes are linked. These priority queues  are  mapped  by
     the  system  configuration  into  a set of global scheduling
     priorities which  are  available  to  processes  within  the
     class. (The dispatcher always selects for execution the pro-
     cess with the highest global scheduling priority in the sys-
     tem.)  The priority queues associated with a given class are
     viewed by that class as a contiguous set of priority  levels
     numbered  from  0 (lowest priority) to n (highest priority-a
     configuration-dependent value). The set of global scheduling
     priorities that the queues for a given class are mapped into
     might not start at zero and might not be contiguous (depend-
     ing on the configuration).

     Processes in the time-sharing class  which  are  running  in
     user  mode  (or  in  kernel  mode before going to sleep) are
     scheduled according to  the  parameters  in  a  time-sharing
     dispatcher  parameter  table  (ts_dptbl).  Processes  in the
     inter-active scheduling class are also  scheduled  according
     to  the  parameters in the time-sharing dispatcher parameter
     table. (Time-sharing processes  and  inter-active  processes
     running  in kernel mode after sleeping are run within a spe-
     cial range of priorities reserved for such processes and are
     not  affected  by  the parameters in the ts_dptbl until they
     return to user mode.) The  ts_dptbl  consists  of  an  array
     (config_ts_dptbl[])    of   parameter   structures   (struct
     tsdpent_t), one for each of the n priority  levels  used  by
     time-sharing  processes  and  inter-active processes in user
     mode. The structures are accessed via a pointer, (ts_dptbl),
     to the array. The properties of a given priority level i are
     specified by the  ith  parameter  structure  in  this  array
     (ts_dptbl[ i] ).

     A parameter structure consists  of  the  following  members.
     These   are  also  described  in  the  /usr/include/sys/ts.h
     header.

     ts_globpri
           The global scheduling priority  associated  with  this
           priority   level.  The  mapping  between  time-sharing
           priority levels and global  scheduling  priorities  is
           determined  at  boot time by the system configuration.
           ts_globpri is the only member of  the  ts_dptbl  which



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File Formats                                          ts_dptbl(4)



           cannot be changed with dispadmin(1M).

     ts_quantum
           The length of the time quantum allocated to  processes
           at this level in ticks (hz).

           In the high resolution clock mode (hires_tick  set  to
           1),  the value of hz is set to 1000. Increase quantums
           to maintain the same absolute time quantums.

     ts_tqexp
           Priority level of the new queue on which  to  place  a
           process running at the current level if it exceeds its
           time quantum. Normally this field  links  to  a  lower
           priority time-sharing level that has a larger quantum.

     ts_slpret
           Priority level of the new queue on which  to  place  a
           process,  that  was  previously  in  user mode at this
           level, when it returns to user  mode  after  sleeping.
           Normally  this  field links to a higher priority level
           that has a smaller quantum.

     ts_maxwait
           A per process counter, ts_dispwait is  initialized  to
           zero  each time a time-sharing or inter-active process
           is placed back on the dispatcher queue after its  time
           quantum   has   expired   or   when   it  is  awakened
           (ts_dispwait is not reset to zero when  a  process  is
           preempted  by a higher priority process). This counter
           is incremented once per second for each process  on  a
           dispatcher  or  sleep queue. If a process' ts_dispwait
           value exceeds the ts_maxwait value for its level,  the
           process'  priority  is  changed  to  that indicated by
           ts_lwait. The purpose of  this  field  is  to  prevent
           starvation.

     ts_lwait
           Move  a  process  to  this  new  priority   level   if
           ts_dispwait is greater than ts_maxwait.

     An administrator can affect the behavior of the time-sharing
     portion  of  the  scheduler  by  reconfiguring the ts_dptbl.
     Since  processes  in  the  time-sharing   and   inter-active
     scheduling  classes  share the same dispatch parameter table
     (ts_dptbl), changes to this table will affect both  schedul-
     ing classes. There are two methods available for doing this:
     reconfigure with a loadable module at boot-time or by  using
     dispadmin(1M) at run-time.

  ts_dptbl Loadable Module




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File Formats                                          ts_dptbl(4)



     The ts_dptbl can be  reconfigured  with  a  loadable  module
     which contains a new time sharing dispatch table. The module
     containing the dispatch table is separate from the TS  load-
     able  module which contains the rest of the time-sharing and
     inter-active software. This is the only method that  can  be
     used to change the number of time-sharing priority levels or
     the set of global scheduling priorities used  by  the  time-
     sharing and inter-active classes. The relevant procedure and
     source code is described in the REPLACING THE TS_DPTBL LOAD-
     ABLE MODULE section.

  dispadmin Configuration File
     With the exception of ts_globpri all of the members  of  the
     ts_dptbl  can  be  examined and modified on a running system
     using the dispadmin(1M) command. Invoking dispadmin for  the
     time-sharing  or inter-active class allows the administrator
     to retrieve the  current  ts_dptbl  configuration  from  the
     kernel's  in-core table, or overwrite the in-core table with
     values from a configuration  file.  The  configuration  file
     used  for  input  to  dispadmin must conform to the specific
     format described below.

     Blank lines are ignored and any part of a line to the  right
     of  a # symbol is treated as a comment. The first non-blank,
     non-comment line must indicate the resolution to be used for
     interpreting the ts_quantum time quantum values. The resolu-
     tion is specified as


     RES=res

     where res is a positive integer between 1 and  1,000,000,000
     inclusive  and  the resolution used is the reciprocal of res
     in seconds  (for  example,  RES=1000  specifies  millisecond
     resolution).  Although very fine (nanosecond) resolution may
     be specified, the time quantum lengths are rounded up to the
     next integral multiple of the system clock's resolution.

     The remaining lines in the file  are  used  to  specify  the
     parameter  values for each of the time-sharing priority lev-
     els. The first  line  specifies  the  parameters  for  time-
     sharing  level  0,  the second line specifies the parameters
     for time-sharing level 1, etc. There  must  be  exactly  one
     line for each configured time-sharing priority level.

EXAMPLES
     Example 1: A Sample From a Configuration File

     The following excerpt from a  dispadmin  configuration  file
     illustrates the format. Note that for each line specifying a
     set  of  parameters  there  is  a  comment  indicating   the
     corresponding  priority  level. These level numbers indicate



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File Formats                                          ts_dptbl(4)



     priority within the time-sharing  and  interactive  classes,
     and  the  mapping  between these time-sharing priorities and
     the corresponding global scheduling priorities is determined
     by  the  configuration  specified in the ts master file. The
     level numbers  are  strictly  for  the  convenience  of  the
     administrator  reading  the  file  and, as with any comment,
     they are ignored by dispadmin. dispadmin  assumes  that  the
     lines  in  the  file  are ordered by consecutive, increasing
     priority level (from  0  to  the  maximum  configured  time-
     sharing  priority). The level numbers in the comments should
     normally agree with this ordering; if for some  reason  they
     don't, however, dispadmin is unaffected.

     # Time-Sharing Dispatcher Configuration File RES=1000


     # ts_quantum  ts_tqexp  ts_slpret  ts_maxwait  ts_lwait  PRIORITY
     #                                                         LEVEL
     500            0        10         5           10        # 0
     500            0        11         5           11        # 1
     500            1        12         5           12        # 2
     500            1        13         5           13        # 3
     500            2        14         5           14        # 4
     500            2        15         5           15        # 5
     450            3        16         5           16        # 6
     450            3        17         5           17        # 7
     .              .        .          .           .         . .
     .              .        .          .           .         . .
     .              .        .          .           .         . .
     50             48       59         5           59        # 58
     50             49       59         5           59        # 59

     Example 2: Replacing The ts_dptbl Loadable Module

     In order to change the size of  the  time  sharing  dispatch
     table, the loadable module which contains the dispatch table
     information will have to be built. It  is  recommended  that
     you save the existing module before using the following pro-
     cedure.

     1. Place the dispatch table  code  shown  below  in  a  file
        called ts_dptbl.c An example of this file follows.

     2. Compile the code using the  given  compilation  and  link
        lines supplied.

        cc -c -0 -D_KERNEL
        ts_dptbl.c
        ld -r -o TS_DPTBL ts_dptbl.o


     3. Copy the  current  dispatch  table  in  /kernel/sched  to



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File Formats                                          ts_dptbl(4)



        TS_DPTBL.bak.

     4. Replace the current TS_DPTBL in /kernel/sched.

     5. You will have to make changes in the /etc/system file  to
        reflect  the changes to the sizes of the tables. See sys-
        tem(4). The two variables  affected  are  ts_maxupri  and
        ts_maxkmdpri. The syntax for setting these is as follows:

        set TS:ts_maxupri=(value for max time-sharing user priority)
        set TS:ts_maxkmdpri=(number of kernel mode priorities - 1)


     6. Reboot the system to use the new dispatch table.

     Great care should be used in replacing  the  dispatch  table
     using  this  method.  If you do not get it right, panics may
     result, thus making the system unusable.

     The following is an example of a ts_dptbl.c  file  used  for
     building the new ts_dptbl.

     /* BEGIN ts_dptbl.c */
     #include <sys/proc.h>
     #include <sys/priocntl.h>
     #include <sys/class.h>
     #include <sys/disp.h>
     #include <sys/ts.h>
     #include <sys/rtpriocntl.h>
     /*
      * This is the loadable module wrapper.
      */
     #include <sys/modctl.h>
     extern struct mod_ops mod_miscops;
     /*
      * Module linkage information for the kernel.
      */
     static struct modlmisc modlmisc = {
          &mod_miscops, "Time sharing dispatch table"
     };
     static struct modlinkage modlinkage = {
          MODREV_1, &modlmisc, 0
     };
     _init()
     {
          return (mod_install(&modlinkage));
     }
     _info(modinfop)
          struct modinfo *modinfop;
     {
          return (mod_info(&modlinkage, modinfop));
     }



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File Formats                                          ts_dptbl(4)



     /*
      * array of global priorities used by ts procs sleeping or
      * running in kernel mode after sleep. Must have at least
      * 40 values.
      */
     pri_t config_ts_kmdpris[] = {
              60,61,62,63,64,65,66,67,68,69,
              70,71,72,73,74,75,76,77,78,79,
              80,81,82,83,84,85,86,87,88,89,
              90,91,92,93,94,95,96,97,98,99,
     };
     tsdpent_t config_ts_dptbl[] = {

     /*  glbpri  qntm  tqexp  slprt  mxwt  lwt  */

         0,      100,  0,     10,    5,    10,
         1,      100,  0,     11,    5,    11,
         2,      100,  1,     12,    5,    12,
         3,      100,  1,     13,    5,    13,
         4,      100,  2,     14,    5,    14
         5,      100,  2,     15,    5,    15,
         6,      100,  3,     16,    5,    16,
         7,      100,  3,     17,    5,    17,
         8,      100,  4,     18,    5,    18,
         9,      100,  4,     19,    5,    19,
         10,     80,   5,     20,    5,    20,
         11,     80,   5,     21,    5,    21,
         12,     80,   6,     22,    5,    22,
         13,     80,   6,     23,    5,    23,
         14,     80,   7,     24,    5,    24,
         15,     80,   7,     25,    5,    25,
         16,     80,   8,     26,    5,    26,
         17,     80,   8,     27,    5,    27,
         18,     80,   9,     28,    5,    28,
         19,     80,   9,     29,    5,    29,
         20,     60,   10,    30,    5,    30,
         21,     60,   11,    31,    5,    31,
         22,     60,   12,    32,    5,    33,
         24,     60,   14,    34,    5,    34,
         25,     60,   15,    35,    5,    35,
         26,     60,   16,    36,    5,    36,
         27,     60,   17,    37,    5,    37,
         28,     60,   18,    38,    5,    38,
         29,     60,   19,    39,    5,    39,
         30,     40,   20,    40,    5,    40,
         31,     40,   21,    41,    5,    41,
         32,     40,   22,    42,    5,    42,
         33,     40,   23,    43,    5,    43,
         34,     40,   24,    44,    5,    44,
         35,     40,   25,    45,    5,    45,
         36,     40,   26,    46,    5,    46,
         37,     40,   27,    47,    5,    47,



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File Formats                                          ts_dptbl(4)



         38,     40,   28,    48,    5,    48,
         39,     40,   29,    49,    5,    49,
         40,     20,   30,    50,    5,    50,
         41,     20,   31,    50,    5,    50,
         42,     20,   32,    51,    5,    51,
         43,     20,   33,    51,    5,    51,
         44,     20,   34,    52,    5,    52,
         45,     20,   35,    52,    5,    52,
         46,     20,   36,    53,    5,    53,
         47,     20    37,    53,    5,    53,
         48,     20,   38,    54,    5,    54,
         49,     20,   39,    54,    5,    54,
         50,     10,   40,    55,    5,    55,
         51,     10,   41,    55,    5,    55,
         52,     10,   42,    56,    5,    56,
         53,     10,   43,    56,    5,    56,
         54,     10,   44,    57,    5,    57,
         55,     10,   45,    57,    5,    57,
         56,     10,   46,    58,    5,    58,
         57,     10,   47,    58,    5,    58,
         58,     10,   48,    59,    5,    59,
         59,     10,   49,    59,    5,    59,

     };

     short config_ts_maxumdpri = sizeof (config_ts_dptbl)/16 - 1;
     /*
      * Return the address of config_ts_dptbl
      */
     tsdpent_t *
     ts_getdptbl()
     {
           return (config_ts_dptbl);
     }

     /*
      * Return the address of config_ts_kmdpris
      */
      int *
      ts_getkmdpris()
     {
           return (config_ts_kmdpris);
     }

     /*
      * Return the address of ts_maxumdpri
      */
     short
     ts_getmaxumdpri()
     {
            return (config_ts_maxumdpri);
     }



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File Formats                                          ts_dptbl(4)



     /* END ts_dptbl.c */

SEE ALSO
     priocntl(1), dispadmin(1M), priocntl(2), system(4)

     System Administration Guide: Basic Administration

     Programming Interfaces Guide

NOTES
     dispadmin does some limited sanity checking  on  the  values
     supplied  in  the configuration file. The sanity checking is
     intended to ensure that the new ts_dptbl values do not cause
     the system to panic. The sanity checking does not attempt to
     analyze the effect that the new values will have on the per-
     formance  of the system. Unusual ts_dptbl configurations may
     have a dramatic negative impact on the  performance  of  the
     system.

     No sanity checking is done on the ts_dptbl values  specified
     in  the TS_DPTBL loadable module. Specifying an inconsistent
     or nonsensical ts_dptbl configuration through  the  TS_DPTBL
     loadable  module  could  cause  serious performance problems
     and/or cause the system to panic.































SunOS 5.9           Last change: 15 Oct 2002                    8