SYNOPSIS

       priocntl -l
       priocntl -d [-i idtype] [idlist]
       priocntl -s [-c class] [c.s.o.] [-i idtype] [idlist]
       priocntl -e [-c class] [c.s.o.] command [argument(s)]

DESCRIPTION

       The  priocntl  command sets or displays scheduling parameters for a set
       of processes.  Every running process is member of a  scheduling  class.
       Standard scheduling classes are:

              The time-sharing class (TS), which is usually the default.  Pro-
              cesses in this class are scheduled according to a dynamic prior-
              ity based on the adjustable base priority and fair usage princi-
              ples.  The base priority used with the priocntl command  is  the
              negative of the nice value (see nice(1)); higher base priorities
              mean a higher chance that the process is run.   Base  priorities
              range between -19 and 20.

              The  batch  class (B), whose members are given longer timeslices
              but can be preempted by any time-sharing process.

              The isochronous class (ISO), whose members retain their  dynamic
              priority even if they make heavy use of computing resources.

              The  real time round-robin (fixed priority) scheduling class (RT
              or FP).  Processes that belong to this class have always a fixed
              higher priority than processes in the time-sharing class and are
              scheduled according to a priority value (1 to 99).  Each process
              can  run  for a maximum time quantum and is placed at the end of
              the associated priority list if the time quantum is exceeded.

              The real time first in-first out scheduling class (FF), which is
              similar to the round-robin scheduling class except that no maxi-
              mum time quantum is applied.

       The process usually requires privilegue to get into  one  of  the  real
       time  scheduling classes.  If a process tries this but lacks the privi-
       legue, it will be put into the isochronous class instead.

       See sched_setscheduler(2) for further detail on scheduling classes.

       With the -l option, a list  of  all  available  scheduling  classes  is
       printed along with the associated parameters for each class.

       The  -d  option  causes  the current scheduling parameters for a set of
       processes to be printed.

       The -s option allows to alter the scheduling parameters for  a  set  of
       processes.   To  change  the parameters of the init process (process ID
       1), the -i pid option must be specified with 1 appearing in idlist.

                      present in idlist.

              sid     Selects all processes that belong  to  a  session  whose
                      session id is present in idlist.

              class   idlist  is  interpreted  as a set of scheduling classes;
                      all processes that belong to a given class are selected.

              uid     Selects  all processes whose (numeric) effective user ID
                      appears in idlist .

              gid     Selects all processes whose (numeric) effective group ID
                      appears in idlist .

              all     Selects  all  processes  currently  running.  The idlist
                      arguments are ignored.

       If an -i option is present but no idlist is specified, the process  ID,
       parent process ID etc.  of the priocntl command itself is used.

       The  -c  option  allows to select a scheduling class for processes with
       the -s and -e options (see above for the explanation of valid classes).

       The  class-specific  option is currently -p priority for all scheduling
       classes; it allows to set the  base  or  scheduling  priority  for  the
       process, as described above.

SEE ALSO

       nice(1), renice(1), sched_setscheduler(2), setpriority(2)

NOTES

       Due  to  the  lack  of  a  priocntl() system call on Linux and FreeBSD,
       selection of processes is performed in user space, and there is a  time
       gap  between  selection and the operation of parameter setting with the
       -s option.  For an idlist of other than a single process id, it is thus
       possible that the priocntl command misses processes that are created at
       the time it is running, without being able to inform the user  if  this
       has happened.

       The  batch class and the isochronous class are not available on FreeBSD
       and are currently not part of the mainline Linux kernel;  Con  Kolivas'
       patch set adds support for them.



Heirloom Toolchest                  9/25/04                        PRIOCNTL(1)