PRIOCNTL(1) User Commands PRIOCNTL(1)

NAME

priocntl - display or set scheduling parameters of specified process(es)

SYNOPSIS

priocntl -l


priocntl -d [-i idtype] [idlist]


priocntl -s [-c class] [class-specific options]
[-i idtype] [idlist]


priocntl -e [-c class] [class-specific options] command
[argument(s)]

DESCRIPTION

The priocntl command displays or sets scheduling parameters of the
specified process(es). It can also be used to display the current
configuration information for the system's process scheduler or execute a
command with specified scheduling parameters.


Processes fall into distinct classes with a separate scheduling policy
applied to each class. The process classes currently supported are the
real-time class, time-sharing class, interactive class, fair-share class,
and the fixed priority class. The characteristics of these classes and
the class-specific options they accept are described below in the USAGE
section under the headings Real-Time Class, Time-Sharing Class, Inter-
Active Class, Fair-Share Class, and Fixed-Priority Class. With
appropriate permissions, the priocntl command can change the class and
other scheduling parameters associated with a running process.


In the default configuration, a runnable real-time process runs before
any other process. Therefore, inappropriate use of real-time processes
can have a dramatic negative impact on system performance.


If an idlist is present, it must appear last on the command line and the
elements of the list must be separated by white space. If no idlist is
present, an idtype argument of pid, ppid, pgid, sid, taskid, class, uid,
gid, projid, or zoneid specifies the process ID, parent process ID,
process group ID, session ID, task ID, class, user ID, group ID, project
ID, or zone ID, respectively, of the priocntl command itself.


The command

priocntl -d [-i idtype] [idlist]


displays the class and class-specific scheduling parameters of the
process(es) specified by idtype and idlist.


The command

priocntl -s [-c class] [class-specific options] \
[-i idtype] [idlist]


sets the class and class-specific parameters of the specified processes
to the values given on the command line. The -c class option specifies
the class to be set. (The valid class arguments are RT for real-time, TS
for time-sharing, IA for inter-active, FSS for fair-share, or FX for
fixed-priority.)


The class-specific parameters to be set are specified by the class-
specific options as explained under the appropriate heading below. If the
-c class option is omitted, idtype and idlist must specify a set of
processes which are all in the same class, otherwise an error results. If
no class-specific options are specified, the process's class-specific
parameters are set to the default values for the class specified by -c
class (or to the default parameter values for the process's current class
if the -c class option is also omitted).


In order to change the scheduling parameters of a process using priocntl
the real or effective user ID (respectively, groupID) of the user
invoking priocntl must match the real or effective user ID (respectively,
groupID) of the receiving process or the effective user ID of the user
must be super-user. These are the minimum permission requirements
enforced for all classes. An individual class can impose additional
permissions requirements when setting processes to that class or when
setting class-specific scheduling parameters.


When idtype and idlist specify a set of processes, priocntl acts on the
processes in the set in an implementation-specific order. If priocntl
encounters an error for one or more of the target processes, it can or
cannot continue through the set of processes, depending on the nature of
the error.


If the error is related to permissions, priocntl prints an error message
and then continues through the process set, resetting the parameters for
all target processes for which the user has appropriate permissions. If
priocntl encounters an error other than permissions, it does not continue
through the process set but prints an error message and exits
immediately.


A special sys scheduling class exists for the purpose of scheduling the
execution of certain special system processes (such as the swapper
process). It is not possible to change the class of any process to sys.
In addition, any processes in the sys class that are included in the set
of processes specified by idtype and idlist are disregarded by priocntl.
For example, if idtype were uid, an idlist consisting of a zero would
specify all processes with a UID of 0, except processes in the sys class
and (if changing the parameters using the -s option) the init process.


The init process (process ID 1) is a special case. In order for the
priocntl command to change the class or other scheduling parameters of
the init process, idtype must be pid and idlist must be consist of only a
1. The init process can be assigned to any class configured on the
system, but the time-sharing class is almost always the appropriate
choice. Other choices can be highly undesirable; see the System
Administration Guide: Basic Administration for more information.


The command

priocntl -e [-c class] [class-specific options] command \
[argument...]


executes the specified command with the class and scheduling parameters
specified on the command line (arguments are the arguments to the
command). If the -c class option is omitted the command is run in the
user's current class.

OPTIONS

The following options are supported:

-c class
Specifies the class to be set. (The valid class arguments
are RT for real-time, TS for time-sharing, IA for inter-
active, FSS for fair-share, or FX for fixed-priority.) If
the specified class is not already configured, it is
automatically configured.


-d
Displays the scheduling parameters associated with a set of
processes.


-e
Executes a specified command with the class and scheduling
parameters associated with a set of processes.


-i idtype
This option, together with the idlist arguments (if any),
specifies one or more processes to which the priocntl
command is to apply. The interpretation of idlist depends on
the value of idtype. If the -i idtype option is omitted when
using the -d or -s options the default idtype of pid is
assumed.

The valid idtype arguments and corresponding interpretations
of idlist are as follows:

-i all
The priocntl command applies to all existing
processes. No idlist should be specified (if
one is specified, it is ignored). The
permission restrictions described below still
apply.


-i ctid
idlist is a list of process contract IDs. The
priocntl command applies to all processes with
a process contract ID equal to an ID from the
list.


-i class
idlist consists of a single class name (RT for
real-time, TS for time-sharing, IA for inter-
active, FSS for fair-share, or FX for fixed-
priority). The priocntl command applies to all
processes in the specified class.


-i gid
idlist is a list of group IDs. The priocntl
command applies to all processes with an
effective group ID equal to an ID from the
list.


-i pgid
idlist is a list of process group IDs. The
priocntl command applies to all processes in
the specified process groups.


-i pid
idlist is a list of process IDs. The priocntl
command applies to the specified processes.


-i ppid
idlist is a list of parent process IDs. The
priocntl command applies to all processes whose
parent process ID is in the list.


-i projid
idlist is a list of project IDs. The priocntl
command applies to all processes with an
effective project ID equal to an ID from the
list.


-i sid
idlist is a list of session IDs. The priocntl
command applies to all processes in the
specified sessions.


-i taskid
idlist is a list of task IDs. The priocntl
command applies to all processes in the
specified tasks.


-i uid
idlist is a list of user IDs. The priocntl
command applies to all processes with an
effective user ID equal to an ID from the list.


-i zoneid
idlist is a list of zone IDs. The priocntl
command applies to all processes with an
effective zone ID equal to an ID from the list.


-l
Displays a list of the classes currently configured in the
system along with class-specific information about each
class. The format of the class-specific information
displayed is described under USAGE.


-s
Sets the scheduling parameters associated with a set of
processes.


The valid class-specific options for setting real-time parameters are:

-p rtpri
Sets the real-time priority of the specified
process(es) to rtpri.


-t tqntm [-r res]
Sets the time quantum of the specified process(es)
to tqntm. You can optionally specify a resolution as
explained below.


-q tqsig
Sets the real-time time quantum signal of the
specified process(es) to tqsig.


The valid class-specific options for setting time-sharing parameters are:

-m tsuprilim
Sets the user priority limit of the specified process(es)
to tsuprilim.


-p tsupri
Sets the user priority of the specified process(es) to
tsupri.


The valid class-specific options for setting inter-active parameters are:

-m iauprilim
Sets the user priority limit of the specified process(es)
to iauprilim.


-p iaupri
Sets the user priority of the specified process(es) to
iaupri.


The valid class-specific options for setting fair-share parameters are:

-m fssuprilim
Sets the user priority limit of the specified
process(es) to fssuprilim.


-p fssupri
Sets the user priority of the specified process(es) to
fssupri.


The valid class-specific options for setting fixed-priority parameters
are:

-m fxuprilim
Sets the user priority limit of the specified process(es)
to fxuprilim.


-p fxupri
Sets the user priority of the specified process(es) to
fxupri.


-t tqntm
[-r res] Sets the time quantum of the specified
process(es) to tqntm. You can optionally specify a
resolution as explained below.

USAGE

Real-Time Class
The real-time class provides a fixed priority preemptive scheduling
policy for those processes requiring fast and deterministic response and
absolute user/application control of scheduling priorities. If the real-
time class is configured in the system, it should have exclusive control
of the highest range of scheduling priorities on the system. This ensures
that a runnable real-time process is given CPU service before any process
belonging to any other class.


The real-time class has a range of real-time priority (rtpri) values that
can be assigned to processes within the class. Real-time priorities range
from 0 to x, where the value of x is configurable and can be displayed
for a specific installation that has already configured a real-time
scheduler, by using the command

priocntl -l


The real-time scheduling policy is a fixed priority policy. The
scheduling priority of a real-time process never changes except as the
result of an explicit request by the user/application to change the rtpri
value of the process.


For processes in the real-time class, the rtpri value is, for all
practical purposes, equivalent to the scheduling priority of the process.
The rtpri value completely determines the scheduling priority of a real-
time process relative to other processes within its class. Numerically
higher rtpri values represent higher priorities. Since the real-time
class controls the highest range of scheduling priorities in the system,
it is guaranteed that the runnable real-time process with the highest
rtpri value is always selected to run before any other process in the
system.


In addition to providing control over priority, priocntl provides for
control over the length of the time quantum allotted to processes in the
real-time class. The time quantum value specifies the maximum amount of
time a process can run, assuming that it does not complete or enter a
resource or event wait state (sleep). Notice that if another process
becomes runnable at a higher priority, the currently running process can
be preempted before receiving its full time quantum.


The command

priocntl -d [-i idtype] [idlist]


displays the real-time priority, time quantum (in millisecond
resolution), and time quantum signal value for each real-time process in
the set specified by idtype and idlist.


Any combination of the -p, -t [-r], and -q options can be used with
priocntl -s or priocntl -e for the real-time class. If an option is
omitted and the process is currently real-time, the associated parameter
is unaffected. If an option is omitted when changing the class of a
process to real-time from some other class, the associated parameter is
set to a default value. The default value for rtpri is 0 and the default
for time quantum is dependent on the value of rtpri and on the system
configuration; see rt_dptbl(5).


When using the -t tqntm option, you can optionally specify a resolution
using the -r res option. (If no resolution is specified, millisecond
resolution is assumed.) If res is specified, it must be a positive
integer between 1 and 1,000,000,000 inclusively and the resolution used
is the reciprocal of res in seconds. For example, specifying -t 10 -r 100
would set the resolution to hundredths of a second and the resulting time
quantum length would be 10/100 seconds (one tenth of a second). Although
very fine (nanosecond) resolution can be specified, the time quantum
length is rounded up by the system to the next integral multiple of the
system clock's resolution. Requests for time quantums of zero or quantums
greater than the (typically very large) implementation-specific maximum
quantum result in an error.


The real-time time quantum signal can be used to notify runaway real-time
processes about the consumption of their time quantum. Those processes,
which are monitored by the real-time time quantum signal, receive the
configured signal in the event of time quantum expiration. The default
value (0) of the time quantum signal tqsig denotes no signal delivery. A
positive value denotes the delivery of the signal specified by the value.
Like kill(1) and other commands operating on signals, the -q tqsig option
is also able to handle symbolically named signals, like XCPU or KILL.


In order to change the class of a process to real-time (from any other
class), the user invoking priocntl must have super-user privilege. In
order to change the rtpri value or time quantum of a real-time process,
the user invoking priocntl must either be super-user, or must currently
be in the real-time class (shell running as a real-time process) with a
real or effective user ID matching the real or effective user ID of the
target process.


The real-time priority, time quantum, and time quantum signal are
inherited across the fork(2) and exec(2) system calls. When using the
time quantum signal with a user defined signal handler across the exec(2)
system call, the new image must install an appropriate user defined
signal handler before the time quantum expires. Otherwise, unpredictable
behavior would result.

Time-Sharing Class
The time-sharing scheduling policy provides for a fair and effective
allocation of the CPU resource among processes with varying CPU
consumption characteristics. The objectives of the time-sharing policy
are to provide good response time to interactive processes and good
throughput to CPU-bound jobs, while providing a degree of
user/application control over scheduling.


The time-sharing class has a range of time-sharing user priority (tsupri)
values that can be assigned to processes within the class. User
priorities range from -x to +x, where the value of x is configurable.
The range for a specific installation can be displayed by using the
command

priocntl -l


The purpose of the user priority is to provide some degree of
user/application control over the scheduling of processes in the time-
sharing class. Raising or lowering the tsupri value of a process in the
time-sharing class raises or lowers the scheduling priority of the
process. It is not guaranteed, however, that a time-sharing process with
a higher tsupri value runs before one with a lower tsupri value. This is
because the tsupri value is just one factor used to determine the
scheduling priority of a time-sharing process. The system can dynamically
adjust the internal scheduling priority of a time-sharing process based
on other factors such as recent CPU usage.


In addition to the system-wide limits on user priority (displayed with
priocntl -l), there is a per process user priority limit (tsuprilim),
which specifies the maximum tsupri value that can be set for a given
process.


The command

priocntl -d [-i idtype] [idlist]


displays the user priority and user priority limit for each time-sharing
process in the set specified by idtype and idlist.


Any time-sharing process can lower its own tsuprilim (or that of another
process with the same user ID). Only a time-sharing process with super-
user privilege can raise a tsuprilim. When changing the class of a
process to time-sharing from some other class, super-user privilege is
required in order to set the initial tsuprilim to a value greater than
zero.


Any time-sharing process can set its own tsupri (or that of another
process with the same user ID) to any value less than or equal to the
process's tsuprilim. Attempts to set the tsupri above the tsuprilim
(and/or set the tsuprilim below the tsupri) result in the tsupri being
set equal to the tsuprilim.


Any combination of the -m and -p options can be used with priocntl -s or
priocntl -e for the time-sharing class. If an option is omitted and the
process is currently time-sharing, the associated parameter is normally
unaffected. The exception is when the -p option is omitted and -m is used
to set a tsuprilim below the current tsupri. In this case, the tsupri is
set equal to the tsuprilim which is being set. If an option is omitted
when changing the class of a process to time-sharing from some other
class, the associated parameter is set to a default value. The default
value for tsuprilim is 0 and the default for tsupri is to set it equal to
the tsuprilim value which is being set.


The time-sharing user priority and user priority limit are inherited
across the fork(2) and exec(2) system calls.

Inter-Active Class
The inter-active scheduling policy provides for a fair and effective
allocation of the CPU resource among processes with varying CPU
consumption characteristics while providing good responsiveness for user
interaction. The objectives of the inter-active policy are to provide
good response time to interactive processes and good throughput to
CPU-bound jobs. The priorities of processes in the inter-active class can
be changed in the same manner as those in the time-sharing class, though
the modified priorities continue to be adjusted to provide good
responsiveness for user interaction.


The inter-active user priority limit, iaupri, is equivalent to tsupri.
The inter-active per process user priority, iauprilim, is equivalent to
tsuprilim.


Inter-active class processes that have the iamode ("interactive mode")
bit set are given a priority boost value of 10, which is factored into
the user mode priority of the process when that calculation is made, that
is, every time a process's priority is adjusted. This feature is used by
the X windowing system, which sets this bit for those processes that run
inside of the current active window to give them a higher priority.

Fair-Share Class
The fair-share scheduling policy provides a fair allocation of system CPU
resources among projects, independent of the number of processes they
own. Projects are given "shares" to control their entitlement to CPU
resources. Resource usage is remembered over time, so that entitlement is
reduced for heavy usage, and increased for light usage, with respect to
other projects. CPU time is scheduled among processes according to their
owner's entitlements, independent of the number of processes each project
owns.


The FSS scheduling class supports the notion of per-process user priority
and user priority limit for compatibility with the time-share scheduler.
The fair share scheduler attempts to provide an evenly graded effect
across the whole range of user priorities. Processes with negative
fssupri values receive time slices less frequently than normal, while
processes with positive fssupri values receive time slices more
frequently than normal. Notice that user priorities do not interfere
with shares. That is, changing a fssupri value of a process is not going
to affect its project's overall CPU usage which only relates to the
amount of shares it is allocated compared to other projects.


The priorities of processes in the fair-share class can be changed in the
same manner as those in the time-share class.

Fixed-Priority Class
The fixed-priority class provides a fixed priority preemptive scheduling
policy for those processes requiring that the scheduling priorities do
not get dynamically adjusted by the system and that the user/application
have control of the scheduling priorities.


The fixed-priority class shares the same range of scheduling priorities
with the time-sharing class, by default. The fixed-priority class has a
range of fixed-priority user priority (fxupri) values that can be
assigned to processes within the class. User priorities range from 0 to
x, where the value of x is configurable. The range for a specific
installation can be displayed by using the command

priocntl -l


The purpose of the user priority is to provide user/application control
over the scheduling of processes in the fixed-priority class. For
processes in the fixed-priority class, the fxupri value is, for all
practical purposes, equivalent to the scheduling priority of the
process. The fxupri value completely determines the scheduling priority
of a fixed-priority process relative to other processes within its class.
Numerically higher fxupri values represent higher priorities.


In addition to the system-wide limits on user priority (displayed with
priocntl -l), there is a per process user priority limit (fxuprilim),
which specifies the maximum fxupri value that can be set for a given
process.


Any fixed-priority process can lower its own fxuprilim (or that of
another process with the same user ID). Only a process with super-user
privilege can raise a fxuprilim. When changing the class of a process to
fixed-priority from some other class, super-user privilege is required in
order to set the initial fxuprilim to a value greater than zero.


Any fixed-priority process can set its own fxupri (or that of another
process with the same user ID) to any value less than or equal to the
process's fxuprilim. Attempts to set the fxupri above the fxuprilim (or
set the fxuprilim below the fxupri) result in the fxupri being set equal
to the fxuprilim.


In addition to providing control over priority, priocntl provides for
control over the length of the time quantum allotted to processes in the
fixed-priority class. The time quantum value specifies the maximum amount
of time a process can run, before surrendering the CPU, assuming that it
does not complete or enter a resource or event wait state (sleep). Notice
that if another process becomes runnable at a higher priority, the
currently running process can be preempted before receiving its full time
quantum.


Any combination of the -m, -p, and -t options can be used with priocntl
-s or priocntl -e for the fixed-priority class. If an option is omitted
and the process is currently fixed-priority, the associated parameter is
normally unaffected. The exception is when the -p option is omitted and
the -m option is used to set a fxuprilim below the current fxupri. In
this case, the fxupri is set equal to the fxuprilim which is being set.
If an option is omitted when changing the class of a process to fixed-
priority from some other class, the associated parameter is set to a
default value. The default value for fxuprilim is 0. The default for
fxupri is to set it equal to the fxuprilim value which is being set. The
default for time quantum is dependent on the fxupri and on the system
configuration. See fx_dptbl(5).


The time quantum of processes in the fixed-priority class can be
changed in the same manner as those in the real-time class.


The fixed-priority user priority, user priority limit, and time quantum
are inherited across the fork(2) and exec(2) system calls.

EXAMPLES

The following are real-time class examples:

Example 1: Setting the Class

The following example sets the class of any non-real-time processes
selected by idtype and idlist to real-time and sets their real-time
priority to the default value of 0. The real-time priorities of any
processes currently in the real-time class are unaffected. The time
quantums of all of the specified processes are set to 1/10 seconds.


example% priocntl -s -c RT -t 1 -r 10 -i idtype idlist

Example 2: Executing a Command in Real-time

The following example executes command in the real-time class with a
real-time priority of 15 and a time quantum of 20 milliseconds:


example% priocntl -e -c RT -p 15 -t 20 command

Example 3: Executing a Command in Real-time with a Specified Quantum

Signal


The following example executes command in the real-time class with a
real-time priority of 11, a time quantum of 250 milliseconds, and where
the specified real-time quantum signal is SIGXCPU:


example% priocntl -e -c RT -p 11 -t 250 -q XCPU command


The following are time-sharing class examples:

Example 4: Setting the Class of non-time-sharing Processes

The following example sets the class of any non-time-sharing processes
selected by idtype and idlist to time-sharing and sets both their user
priority limit and user priority to 0. Processes already in the time-
sharing class are unaffected.


example% priocntl -s -c TS -i idtype idlist

Example 5: Executing a Command in the Time-sharing Class

The following example executes command with the arguments arguments in
the time-sharing class with a user priority limit of 0 and a user
priority of -15:


example% priocntl -e -c TS -m 0 -p -15 command [arguments]

Example 6: Executing a Command in Fixed-Priority Class

The following example executes a command in the fixed-priority class
with a user priority limit of 20 and user priority of 10 and time quantum
of 250 milliseconds:


example% priocntl -e -c FX -m 20 -p 10 -t 250 command

EXIT STATUS

The following exit values are returned:


For options -d, -l, and -s:

0
Successful operation.


1
Error condition.


For option -e:


Return of the Exit Status of the executed command denotes successful
operation. Otherwise,

1
Command could not be executed at the specified priority.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|CSI | Enabled |
+---------------+-----------------+

SEE ALSO

kill(1), nice(1), ps(1), exec(2), fork(2), priocntl(2), FSS(4),
fx_dptbl(5), process(5), rt_dptbl(5), attributes(7), zones(7),
dispadmin(8)


System Administration Guide: Basic Administration

DIAGNOSTICS

priocntl prints the following error messages:

Process(es) not found

None of the specified processes exists.


Specified processes from different classes

The -s option is being used to set parameters, the -c class option is
not present, and processes from more than one class are specified.


Invalid option or argument

An unrecognized or invalid option or option argument is used.


April 1, 2008 PRIOCNTL(1)