System Administration Guide

Timesharing Parameter Table

A default version of the ts_dptb, is delivered with the system in /kernel/sched/TS_DPTBL. The default configuration has 60 timesharing priorities.

The dispadmin -c TS -g command displays a sample ts_dptbl table.


$ dispadmin -c TS -g
# Time Sharing Dispatcher Configuration
RES=1000
 
# ts_quantum  ts_tqexp  ts_slpret  ts_maxwait ts_lwait  PRIORITY LEVEL
       200         0        50           0        50        #     0
       200         0        50           0        50        #     1
       200         0        50           0        50        #     2
       200         0        50           0        50        #     3
       200         0        50           0        50        #     4
       200         0        50           0        50        #     5
       200         0        50           0        50        #     6
       200         0        50           0        50        #     7
       200         0        50           0        50        #     8
       200         0        50           0        50        #     9
       160         0        51           0        51        #    10
       160         1        51           0        51        #    11
       160         2        51           0        51        #    12
       160         3        51           0        51        #    13
       160         4        51           0        51        #    14
       160         5        51           0        51        #    15
       160         6        51           0        51        #    16
       160         7        51           0        51        #    17
       160         8        51           0        51        #    18
       160         9        51           0        51        #    19
       120        10        52           0        52        #    20
       120        11        52           0        52        #    21
       120        12        52           0        52        #    22
       120        13        52           0        52        #    23
       120        14        52           0        52        #    24
       120        15        52           0        52        #    25
       120        16        52           0        52        #    26
       120        17        52           0        52        #    27
       120        18        52           0        52        #    28
       120        19        52           0        52        #    29
        80        20        53           0        53        #    30
        80        21        53           0        53        #    31
        80        22        53           0        53        #    32
        80        23        53           0        53        #    33
        80        24        53           0        53        #    34
        80        25        54           0        54        #    35
        80        26        54           0        54        #    36
        80        27        54           0        54        #    37
        80        28        54           0        54        #    38
        80        29        54           0        54        #    39
        40        30        55           0        55        #    40
        40        31        55           0        55        #    41
        40        32        55           0        55        #    42
        40        33        55           0        55        #    43
        40        34        55           0        55        #    44
        40        35        56           0        56        #    45
        40        36        57           0        57        #    46
        40        37        58           0        58        #    47
        40        38        58           0        58        #    48
        40        39        58           0        59        #    49
        40        40        58           0        59        #    50
        40        41        58           0        59        #    51
        40        42        58           0        59        #    52
        40        43        58           0        59        #    53
        40        44        58           0        59        #    54
        40        45        58           0        59        #    55
        40        46        58           0        59        #    56
        40        47        58           0        59        #    57
        40        48        58           0        59        #    58
        20        49        59       32000        59        #    59
$ 

Table 67-3 describes the fields in the ts_dptbl table.

Table 67-3 Fields in the ts_dptbl Table

Field Name 

Description 

ts_quantum

(runtime) 

Contains the time slice (in milliseconds by default) that a process at a given priority is allowed to run before the scheduler reevaluates its priority. If the process uses up its entire time slice, it is put on the expired-level (ts_tqexp) queue. Time slices run from 40 milliseconds for the highest priority (59) to 200 milliseconds (0) for the lowest priority.

ts_tqexp

(expired level) 

Determines the new process priority for a process whose time slice has expired. If a process uses its whole time slice without sleeping, the scheduler changes its priority to the level indicated in the ts_tqexp column. The expired level is lower than the prior level. For example, a process with a priority of 30 that used up its time slice (80 milliseconds) will get a new priority of 20.

ts_slpret

(sleep level)  

Determines the priority assigned to a process when it returns from sleep. A process may sleep during certain system calls or when waiting for I/O (for example, servicing a page fault or waiting for a lock). When a process returns from sleep, it is always a given a priority of 59.

ts_maxwait

(wait time)  

Specifies the number of seconds a process will be left on a dispatch queue without its time slice expiring. If it does not use its time slice (in ts_maxwait seconds), its new priority will be set to ts_lwait. This is used to prevent a low-priority process from being starved of CPU time.

ts_lwait

(wait level)  

Contains the new priority for a ready-to-run process that has exceeded the maximum wait time (ts_maxwait) without getting its full time slice.

PRIORITY LEVEL

Contains global priorities. Processes put in queues at the higher priority levels run first. The global priorities run from a high of 59 to a low of 0. This is the only column in the table that is not tunable.