Managing Process Class Information
The following list identifies the process scheduling classes that can be configured on
your system. Also included is the user priority range for the timesharing class.
The possible process scheduling classes are as follows:
Fair share (FSS)
Fixed (FX)
System (SYS)
Interactive (IA)
Real-time (RT)
Timesharing (TS)
The user-supplied priority ranges from -60 to +60.
The priority of a process is inherited from the parent process. This priority is referred to as the user-mode priority.
The system looks up the user-mode priority in the timesharing dispatch parameter table. Then, the system adds in any nice or priocntl (user-supplied) priority and ensures a 0–59 range to create a global priority.
Changing the Scheduling Priority of Processes (priocntl)
The scheduling priority of a process is the priority assigned by the process
scheduler, according to scheduling policies. The dispadmin command lists the default scheduling policies. For
more information, see the dispadmin(1M) man page.
You can use the priocntl command to assign processes to a priority
class and to manage process priorities. For instructions on using the priocntl command to
manage processes, see How to Designate a Process Priority (priocntl).
How to Display Basic Information About Process Classes (priocntl)
- Display process scheduling classes and priority ranges with the priocntl -l command.
$ priocntl -l
Example 12-5 Displaying Basic Information About Process Classes (
priocntl)
The following example shows output from the priocntl -l command.
# priocntl -l
CONFIGURED CLASSES
==================
SYS (System Class)
TS (Time Sharing)
Configured TS User Priority Range: -60 through 60
FX (Fixed priority)
Configured FX User Priority Range: 0 through 60
IA (Interactive)
Configured IA User Priority Range: -60 through 60
How to Display the Global Priority of a Process
Example 12-6 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 the sh
process has the lowest priority.
$ 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)
- (Optional) Assume the Primary Administrator role, or become superuser.
The Primary Administrator role includes the Primary Administrator profile. To create the role
and assign the role to a user, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
- Start a process with a designated priority.
# priocntl -e -c class -m user-limit -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), and FX (fixed priority).
- -m user-limit
When you use the -p option, specifies the maximum amount you can raise or lower your priority,
- -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.
- Verify the process status.
# ps -ecl | grep command-name
Example 12-7 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)
- (Optional) Assume the Primary Administrator role, or become superuser.
The Primary Administrator role includes the Primary Administrator profile. To create the role
and assign the role to a user, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
- Change the scheduling parameters of a running timesharing process.
# priocntl -s -m user-limit [-p user-priority] -i idtype idlist
- -s
Lets you set the upper limit on the user priority range and change the current priority.
- -m user-limit
When you use the -p option, specifies the maximum amount you can raise or lower the priority.
- -p user-priority
Allows you to designate a priority.
- -i xidtype xidlist
Uses a combination of xidtype and xidlist to identify the process or processes. The xidtype specifies the type of ID, such as the process ID or the user ID. Use xidlist to identify a list of process IDs or user IDs.
- Verify the process status.
# ps -ecl | grep idlist
Example 12-8 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 -m 500 -p 20 myprog
# ps -ecl | grep myprog
How to Change the Class of a Process (priocntl)
- (Optional) Become superuser or assume an equivalent role.
- 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 for time-sharing or RT for real-time, to which you are changing the process.
- -i idtype idlist
Uses a combination of xidtype and xidlist to identify the process or processes. The xidtype specifies the type of ID, such as the process ID or user ID. Use xidlist to identify a list of process IDs or user IDs.
Note - You must be superuser or working in a real-time shell to change a
process from, or to, a real-time process. 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.
- Verify the process status.
# ps -ecl | grep idlist
Example 12-9 Changing the Class of a Process (
priocntl)
The following example shows how to change all the processes that belong to
user 15249 to real-time processes.
# priocntl -s -c RT -i uid 15249
# ps -ecl | grep 15249
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.
The priority number is determined by several factors, including the process's 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. However, 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 from 0 to +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)
Using this procedure, a user can lower the priority of a process.
However, superuser can raise or lower the priority of a process.
Note - This section describes the syntax of the /usr/bin/nice command and not the C-shell
built-in nicecommand. For information about the C-shell nice command, see the csh(1) man
page.
- Determine whether you want to change the priority of a process, either as
a user or as superuser. Then, select one of the following:
- As a user, follow the examples in Step 2 to lower the
priority of a command.
- As a superuser, follow the examples in Step 3 to raise or
lower priorities of a command.
- 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
- As superuser or assuming an equivalent role, 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
See Also
For more information, see the nice(1) man page.
