priocntl(1) User Commands priocntl(1)NAMEpriocntl - display or set scheduling parameters of specified processes
and LWPs
SYNOPSISpriocntl-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 processes or LWPs.. It can also be used to display the cur‐
rent configuration information for the system's process scheduler or
execute a command with specified scheduling parameters.
Processes and LWPs fall into distinct classes with a separate schedul‐
ing policy applied to each class. The 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 or
LWPs.
In the default configuration, a runnable real-time process or LWP runs
before any other process. Therefore, inappropriate use of real-time
processes or LWPs can have a dramatic negative impact on system perfor‐
mance.
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
or LWP 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-spe‐
cific options as explained under the appropriate heading below. If the
-c class option is omitted, idtype and idlist must specify a set of
processes or LWPs 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).
To change the scheduling parameters of a process or LWP using priocntl
the real or effective user ID (respectively, groupID) of the user
invoking priocntl must match the real or effective user ID (respec‐
tively, groupID) of the receiving process or LWP, 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, with or without a
list of LWPs, priocntl acts on the processes in the set in an implemen‐
tation-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 mes‐
sage and then continues through the process set, resetting the parame‐
ters for all target processes for which the user has appropriate per‐
missions. 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 or LWPs in the sys class that are specified
by idtype and idlist are disregarded by priocntl. For example, if
idtype were uid, an idlist consisting of a zero would specify all pro‐
cesses 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 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 com‐
mand). 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 auto‐
matically 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 or LWPs to which the pri‐
ocntl 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 interpreta‐
tions of idlist are as follows:
-i all The priocntl command applies to all exist‐
ing processes. No idlist should be speci‐
fied (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 pro‐
cesses 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 prioc‐
ntl 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[/lwp] idlist is a list of process IDs, possitble
followed by a list of LWPs (lightweight
processes). The priocntl command applies
to the specified processes and LWPs.
-i ppid idlist is a list of parent process IDs.
The priocntl command applies to all pro‐
cesses whose parent process ID is in the
list.
-i projid idlist is a list of project IDs. The pri‐
ocntl 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 pri‐
ocntl 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 dis‐
played 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 pro‐
cesses and LWPs 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 processes and LWPs to tqsig.
The valid class-specific options for setting time-sharing parameters
are:
-m tsuprilim Sets the user priority limit of the specified processes
and LWPs to tsuprilim.
-p tsupri Sets the user priority of the specified processes and
LWPs to tsupri.
The valid class-specific options for setting inter-active parameters
are:
-m iauprilim Sets the user priority limit of the specified processes
and LWPs to iauprilim.
-p iaupri Sets the user priority of the specified processes and
LWPs to iaupri.
The valid class-specific options for setting fair-share parameters are:
-m fssuprilim Sets the user priority limit of the specified pro‐
cesses and LWPs to fssuprilim.
-p fssupri Sets the user priority of the specified processes and
LWPs to fssupri.
The valid class-specific options for setting fixed-priority parameters
are:
-m fxuprilim Sets the user priority limit of the specified processes
and LWPs to fxuprilim.
-p fxupri Sets the user priority of the specified processes and
LWPs to fxupri.
-t tqntm [-r res] Sets the time quantum of the specified pro‐
cesses and LWPs 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 priori‐
ties 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 sched‐
uling 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 prac‐
tical 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. Numeri‐
cally 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 resolu‐
tion), 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 parame‐
ter 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(4).
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 result‐
ing time quantum length would be 10/100 seconds (one tenth of a sec‐
ond). 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) implementa‐
tion-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 pro‐
cesses, 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 sig‐
nal delivery. A positive value denotes the delivery of the signal spec‐
ified by the value. Like kill(1) and other commands operating on sig‐
nals, 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,
unpredicable 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 con‐
sumption 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/applica‐
tion 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 config‐
urable. 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-shar‐
ing 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 nor‐
mally 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 con‐
sumption 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 pri‐
ority.
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 entitle‐
ment 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 prior‐
ity 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
positive fssupri values receive time slices less frequently than nor‐
mal, while negative nice processes receive time slices more fre‐
quently 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 schedul‐
ing policy for those processes requiring that the scheduling priorities
do not get dynamically adjusted by the system and that the user/appli‐
cation 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 pro‐
cesses in the fixed-priority class, the fxupri value is, for all prac‐
tical 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 receiv‐
ing 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( 4).
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 pri‐
ority 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 quan‐
tum of 250 milliseconds:
example% priocntl-e -c FX -m 20 -p 10 -t 250 command
Example 7 Changing the Priority of a Specific LWP
The following example sets the user priority limit of 20 and user pri‐
ority of 15 for the LWP 5 in process 500:
example% priocntl-s -m 20 -p 15 500/5
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(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcsu │
├─────────────────────────────┼─────────────────────────────┤
│CSI │Enabled │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOkill(1), nice(1), ps(1), dispadmin(1M), exec(2), fork(2), priocntl(2),
fx_dptbl(4), process(4), rt_dptbl(4), attributes(5), zones(5), FSS(7)DIAGNOSTICSpriocntl 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 speci‐
fied.
Invalid option or argument
An unrecognized or invalid option or option argument is used.
SunOS 5.10 1 May 2011 priocntl(1)
