Process scheduling

Changing scheduler parameters with dispadmin

The dispadmin(1M) command allows you to change or retrieve scheduler information in a running system. Changes made using dispadmin remain only until a reboot; then the values are reset. To make permanent configuration changes, you must change the scheduler parameter tables in the /etc/conf/pack.d directory, as described in ``Installing a fixed priority scheduler class''. However, you can use dispadmin to get an effect equivalent to changing configuration tables by calling dispadmin from a startup script that changes the configuration automatically at boot time.

The dispadmin command has three forms:

dispadmin -l: lists the configured scheduler classes.
dispadmin -c class -g [-r res]: gets scheduler parameters for the specified class. By default, time slices are printed in milliseconds. You can optionally retrieve time slices at a resolution specified by the -r option.
dispadmin -c class -s file: sets scheduler parameters for the specified class from file (your configuration file).

Here is the output of dispadmin -l for the default configuration:

   CONFIGURED CLASSES
   ==================
   
   SYS     (System Class)
   FC      (Time Sharing)
   TS      (Time Sharing)
   FP      (Fixed Priority)

The -g option gets current scheduler parameters for the specified class and writes them to the standard output. Scheduler parameters are class specific. The parameters for the default classes are described in the previous sections about the scheduler parameter tables; ts_dptbl holds time-sharing parameters, fc_dptbl holds fixed class parameters, and fp_dptbl holds fixed priority parameters.

The following screen shows part of the output of dispadmin -g -c FP (for the fixed priority class):

# Fixed Priority Dispatcher Configuration RES=1000

# TIME QUANTUM PRIORITY # (fp_quantum) LEVEL 1000 # 0 1000 # 1 1000 # 2 1000 # 3 1000 # 4 1000 # 5 1000 # 6 1000 # 7 1000 # 8 1000 # 9 800 # 10 800 # 11 800 # 12 ... ... 100 # 50

The following screen shows part of the output of dispadmin -g -c TS (for the time-sharing class):

# Time Sharing Dispatcher Configuration RES=1000

# ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait PRIORITY LEVEL 1000 0 10 5 10 # 0 1000 0 11 5 11 # 1 1000 1 12 5 12 # 2 1000 1 13 5 13 # 3 1000 2 14 5 14 # 4 1000 2 15 5 15 # 5 1000 3 16 5 16 # 6 1000 3 17 5 17 # 7 1000 4 18 5 18 # 8 1000 4 19 5 19 # 9 800 5 20 5 20 # 10 800 5 21 5 21 # 11 ... ... ... ... ... ... 100 40 55 5 55 # 50

By default, dispadmin reports time slices in milliseconds. If you specify the -r res option, dispadmin reports time slices in units of res intervals per second. For example, a res of 1000000 reports time slices in microseconds (millionths of a second).

The -s config_file option uses config_file to set scheduler parameters for the specified class. The configuration file must be in the class-specific format produced by the -g option. The meanings of the parameters are described in the previous sections about the scheduler parameter tables; ts_dptbl holds time-sharing parameters, fc_dptbl holds fixed class parameters, and fp_dptbl holds fixed priority parameters.

The following examples show how to set the parameters for the default classes as specified in the configuration files fp_config, fc_config, and ts_config. The examples presuppose that these files are in the correct formats.

Set fixed priority parameters:

dispadmin -c FP -s fp_config

Set fixed class parameters:

dispadmin -c FC -s fc_config

Set time-sharing parameters:

dispadmin -c TS -s ts_config

The files that specify the new scheduler parameters must have the same number of priority levels as the current table that is being overwritten. To change the number of priority levels, you must change the configuration file /etc/conf/pack.d/ts/space.c or /etc/conf/pack.d/fc/space.c or /etc/conf/pack.d/fp/space.c as described in ``Changing scheduler configuration''.