SCHEDRRGETINTERVAL(2) Linux Programmer's Manual SCHEDRRGETINTERVAL(2)

NAME
       schedrrgetinterval - get the SCHEDRR interval for the named process

SYNOPSIS
       #include 

       int schedrrgetinterval(pidt pid, struct timespec * tp);

DESCRIPTION
       schedrrgetinterval()  writes  into the timespec structure pointed to
       by tp the round-robin time quantum for the process identified  by  pid.
       The  specified  process should be running under the SCHEDRR scheduling
       policy.

       The timespec structure has the following form:

           struct timespec {
               timet tvsec;    /* seconds */
               long   tvnsec;   /* nanoseconds */
           };

       If pid is zero, the time quantum for the  calling  process  is  written
       into *tp.

RETURN VALUE
       On  success,  schedrrgetinterval()  returns  0.   On  error,  -1  is
       returned, and errno is set appropriately.

ERRORS
       EFAULT Problem with copying information to user space.

       EINVAL Invalid pid.

       ENOSYS The system call is not yet implemented (only on rather old  ker‐
              nels).

       ESRCH  Could not find a process with the ID pid.

CONFORMING TO
       POSIX.1-2001.

NOTES
       POSIX  systems  on  which  schedrrgetinterval()  is available define
       POSIXPRIORITYSCHEDULING in .

   Linux notes
       POSIX does not specify any mechanism for controlling the  size  of  the
       round-robin  time quantum.  Older Linux kernels provide a (nonportable)
       method of doing this.  The quantum can be controlled by  adjusting  the
       process's nice value (see setpriority(2)).  Assigning a negative (i.e.,
       high) nice value results in a  longer  quantum;  assigning  a  positive
       (i.e., low) nice value results in a shorter quantum.  The default quan‐
       tum is 0.1 seconds; the degree to which changing the nice value affects
       the quantum has varied somewhat across kernel versions.  This method of
       adjusting the quantum was removed starting with Linux 2.6.24.

       Linux 3.9 added  a  new  mechanism  for  adjusting  (and  viewing)  the
       SCHEDRR   quantum:   the  /proc/sys/kernel/schedrrtimeslicems  file
       exposes the quantum as a  millisecond  value,  whose  default  is  100.
       Writing 0 to this file resets the quantum to the default value.

SEE ALSO
       schedsetscheduler(2) has a description of the Linux scheduling scheme.

       Programming  for  the  real  world  -  POSIX.4  by Bill O. Gallmeister,
       O'Reilly & Associates, Inc., ISBN 1-56592-074-0.

COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2013-03-18          SCHEDRRGETINTERVAL(2)