How to Display the Global Priority of a Process

You can display the global priority of a process by using the ps command.

$ ps -ecl

The global priority is listed under the PRI column.

Example--Displaying the Global Priority of a Process

The following example shows ps -ecl command output. The values in the PRI column show that the pageout process has the highest priority, while sh has the lowest.

$ ps -ecl
 F S UID PID  PPID CLS PRI  ADDR      SZ  WCHAN    TTY      TIME   COMD
19 T 0   0    0    SYS 96   f00d05a8   0           ?        0:03  sched
 8 S 0   1    0    TS  50   ff0f4678 185  ff0f4848 ?       36:51   init
19 S 0   2    0    SYS 98   ff0f4018   0  f00c645c ?        0:01 pageout
19 S 0   3    0    SYS 60   ff0f5998   0  f00d0c68 ?      241:01 fsflush
 8 S 0   269  1    TS  58   ff0f5338 303  ff49837e ?        0:07    sac
 8 S 0   204  1    TS  43   ff2f6008  50  ff2f606e console  0:02     sh

How to Designate a Process Priority (priocntl)

1. Become superuser.

2. Start a process with a designated priority.

   # priocntl -e -c class -m userlimit -p pri command-name

   
   

   -e	Executes the command.
   -c class	Specifies the class within which to run the process. The valid classes are TS (timesharing), RT (real time), IA (interactive), FSS (fair share), or FX (fixed priority).
   -m userlimit	Specifies the maximum amount you can raise or lower your priority, when using the -p option.
   -p pri command-name	Lets you specify the relative priority in the RT class, for a real-time thread. For a timesharing process, the -p option lets you specify the user-supplied priority, which ranges from -60 to +60.

3. Verify the process status.

   # ps -ecl | grep command-name

   
   

Example--Designating a Process Priority (priocntl)

The following example shows how to start the find command with the highest possible user-supplied priority.

# priocntl -e -c TS -m 60 -p 60 find . -name core -print
# ps -ecl | grep find

How to Change Scheduling Parameters of a Timesharing Process (priocntl)

1. Become superuser.

2. Change the scheduling parameters of a running timesharing process.

   # priocntl -s -m userlimit [-p userpriority] -i idtype idlist

   
   

   -s	Lets you set the upper limit on the user priority range and change the current priority.
   -m userlimit	Specifies the maximum amount you can raise or lower your priority, when you use the -p option.
   -p userpriority	Allows you to designate a priority.
   -i idtype idlist	Uses a combination of idtype and idlist to identify the process or processes. The idtype specifies the type of ID, such as pid or UID. Use idlist to identify a list of pids or UIDs.

3. Verify the process status.

   # ps -ecl | grep idlist

   
   

Example--Changing Scheduling Parameters of a Timesharing Process (priocntl)

The following example shows how to execute a command with a 500-millisecond time slice, a priority of 20 in the RT class, and a global priority of 120.

# priocntl -e -c RT -t 500 -p 20 myprog
# ps -ecl | grep myprog

How to Change the Class of a Process (priocntl)

1. (Optional) Become superuser.

   ---

   Note - You must be superuser or working in a real-time shell to change a process from, or to, a real-time process.

   ---

2. Change the class of a process.

   # priocntl -s -c class -i idtype idlist

   
   

   -s	Lets you set the upper limit on the user priority range and change the current priority.
   -c class	Specifies the class, TS or RT, to which you are changing the process.
   -i idtype idlist	Uses a combination of idtype and idlist to identify the process or processes. The idtype specifies the type of ID, such as pid or UID. Use idlist to identify a list of pids or UIDs.

3. Verify the process status.

   # ps -ecl | grep idlist

   
   

Example--Changing the Class of a Process (priocntl)

The following example shows how to change all the processes belonging to user 15249 to real-time processes.

# priocntl -s -c RT -i uid 15249
# ps -ecl | grep 15249

Note - If, as superuser, you change a user process to the real-time class, the user cannot subsequently change the real-time scheduling parameters by using the priocntl -s command.

Changing the Priority of a Timesharing Process (nice)

The nice command is only supported for backward compatibility to previous Solaris releases. The priocntl command provides more flexibility in managing processes.

The priority of a process is determined by the policies of its scheduling class, and by its nice number. Each timesharing process has a global priority. The global priority is calculated by adding the user-supplied priority, which can be influenced by the nice or priocntl commands, and the system-calculated priority.

The execution priority number of a process is assigned by the operating system, and is determined by several factors, including its scheduling class, how much CPU time it has used, and in the case of a timesharing process, its nice number.

Each timesharing process starts with a default nice number, which it inherits from its parent process. The nice number is shown in the NI column of the ps report.

A user can lower the priority of a process by increasing its user-supplied priority. But only superuser can lower a nice number to increase the priority of a process. This restriction prevents users from increasing the priorities of their own processes, thereby monopolizing a greater share of the CPU.

The nice numbers range between 0 and +39, with 0 representing the highest priority. The default nice value for each timesharing process is 20. Two versions of the command are available, the standard version, /usr/bin/nice, and the C shell built-in command.

How to Change the Priority of a Process (nice)

Note - This section describes the syntax of the /usr/bin/nice command and not the C-shell nice built-in command. For information about the C-shell nice command, see csh(1).

1. Determine whether you want to lower the priority of a command as a user or raise or lower the priority of a command as superuser and select one of the following:

   • Follow the examples in step 2 to lower the priority of a command as a user.

   • Follow the examples in step 3 to raise or lower priorities of a command as superuser.

2. As a user, lower the priority of a command by increasing the nice number.

   The following nice command executes command-name with a lower priority by raising the nice number by 5 units.

   $ /usr/bin/nice -5 command-name

   
   In the preceding command, the minus sign designates that what follows is an option. This command could also be specified as follows:

   % /usr/bin/nice -n 5 command-name

   
   

   The following nice command lowers the priority of command-name by raising the nice number by the default increment of 10 units, but not beyond the maximum value of 39.

   % /usr/bin/nice command-name

   
   

3. As superuser, raise or lower the priority of a command by changing the nice number.

   The following nice command raises the priority of command-name by lowering the nice number by 10 units, but not below the minimum value of 0.

   # /usr/bin/nice --10 command-name

   
   

   In the preceding command, the first minus sign designates that what follows is an option. The second minus sign indicates a negative number.

   The following nice command lowers the priority of command-name by raising the nice number by 5 units, but not beyond the maximum value of 39.

   # /usr/bin/nice -5 command-name

   
   

For more information, see nice(1).