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man:sched_getattr

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

NAME

     sched_setattr,  sched_getattr  -  set  and  get  scheduling  policy and
     attributes

SYNOPSIS

     #include <sched.h>
     int sched_setattr(pid_t pid, struct sched_attr *attr,
                       unsigned int flags);
     int sched_getattr(pid_t pid, struct sched_attr *attr,
                       unsigned int size, unsigned int flags);

DESCRIPTION

 sched_setattr()
     The sched_setattr() system call sets the scheduling policy and  associ-
     ated  attributes  for  the thread whose ID is specified in pid.  If pid
     equals zero, the scheduling policy and attributes of the calling thread
     will be set.
     Currently,  Linux supports the following "normal" (i.e., non-real-time)
     scheduling policies as values that may be specified in policy:
     SCHED_OTHER   the standard round-robin time-sharing policy;
     SCHED_BATCH   for "batch" style execution of processes; and
     SCHED_IDLE    for running very low priority background jobs.
     Various "real-time" policies are also supported, for special time-crit-
     ical  applications  that  need  precise  control  over the way in which
     runnable threads are selected for execution.  For the  rules  governing
     when  a  process  may  use these policies, see sched(7).  The real-time
     policies that may be specified in policy are:
     SCHED_FIFO    a first-in, first-out policy; and
     SCHED_RR      a round-robin policy.
     Linux also provides the following policy:
     SCHED_DEADLINE
                   a deadline scheduling policy; see sched(7) for details.
     The attr argument is a pointer to a  structure  that  defines  the  new
     scheduling policy and attributes for the specified thread.  This struc-
     ture has the following form:
         struct sched_attr {
             u32 size;              /* Size of this structure */
             u32 sched_policy;      /* Policy (SCHED_*) */
             u64 sched_flags;       /* Flags */
             s32 sched_nice;        /* Nice value (SCHED_OTHER,
                                       SCHED_BATCH) */
             u32 sched_priority;    /* Static priority (SCHED_FIFO,
                                       SCHED_RR) */
             /* Remaining fields are for SCHED_DEADLINE */
             u64 sched_runtime;
             u64 sched_deadline;
             u64 sched_period; };
     The fields of this structure are as follows:
     size   This field should be set to the size of the structure in  bytes,
            as  in  sizeof(struct sched_attr).  If the provided structure is
            smaller than the kernel structure,  any  additional  fields  are
            assumed to be '0'.  If the provided structure is larger than the
            kernel structure, the kernel verifies that all additional fields
            are  0;  if  they  are not, sched_setattr() fails with the error
            E2BIG and updates size to contain the size of the kernel  struc-
            ture.
            The  above  behavior  when the size of the user-space sched_attr
            structure does not match the size of the kernel structure allows
            for  future  extensibility of the interface.  Malformed applica-
            tions that pass oversize structures won't break in the future if
            the  size  of  the kernel sched_attr structure is increased.  In
            the future, it could also allow applications that know  about  a
            larger user-space sched_attr structure to determine whether they
            are running on an older kernel that does not support the  larger
            structure.
     sched_policy
            This  field  specifies  the  scheduling  policy,  as  one of the
            SCHED_* values listed above.
     sched_flags
            This field contains flags controlling scheduling behavior.  Only
            one  such  flag  is currently defined: SCHED_FLAG_RESET_ON_FORK.
            As a result of including this flag, children created by  fork(2)
            do not inherit privileged scheduling policies.  See sched(7) for
            details.
     sched_nice
            This field specifies the nice value to be  set  when  specifying
            sched_policy as SCHED_OTHER or SCHED_BATCH.  The nice value is a
            number in the range -20 (high priority) to +19  (low  priority);
            see sched(7).
     sched_priority
            This field specifies the static priority to be set when specify-
            ing sched_policy as SCHED_FIFO or SCHED_RR.  The  allowed  range
            of  priorities  for  these  policies  can  be  determined  using
            sched_get_priority_min(2)  and  sched_get_priority_max(2).   For
            other policies, this field must be specified as 0.
     sched_runtime
            This field specifies the "Runtime" parameter for deadline sched-
            uling.  The value is expressed in nanoseconds.  This field,  and
            the  next  two fields, are used only for SCHED_DEADLINE schedul-
            ing; for further details, see sched(7).
     sched_deadline
            This field  specifies  the  "Deadline"  parameter  for  deadline
            scheduling.  The value is expressed in nanoseconds.
     sched_period
            This  field specifies the "Period" parameter for deadline sched-
            uling.  The value is expressed in nanoseconds.
     The flags argument is provided to allow for future  extensions  to  the
     interface; in the current implementation it must be specified as 0.
 sched_getattr()
     The  sched_getattr()  system call fetches the scheduling policy and the
     associated attributes for the thread whose ID is specified in pid.   If
     pid  equals  zero,  the scheduling policy and attributes of the calling
     thread will be retrieved.
     The size argument should be set to the size of the sched_attr structure
     as  known  to  user  space.  The value must be at least as large as the
     size of the initially published sched_attr structure, or the call fails
     with the error EINVAL.
     The  retrieved  scheduling  attributes  are placed in the fields of the
     sched_attr structure pointed to by attr.  The kernel sets attr.size  to
     the size of its sched_attr structure.
     If  the  caller-provided  attr  buffer  is  larger  than  the  kernel's
     sched_attr structure, the additional bytes in the user-space  structure
     are  not touched.  If the caller-provided structure is smaller than the
     kernel sched_attr structure and the kernel needs to return values  out-
     side  the  provided  space, sched_getattr() fails with the error E2BIG.
     As with sched_setattr(), these semantics allow for future extensibility
     of the interface.
     The  flags  argument  is provided to allow for future extensions to the
     interface; in the current implementation it must be specified as 0.

RETURN VALUE

     On success, sched_setattr() and sched_getattr() return 0.  On error, -1
     is returned, and errno is set to indicate the cause of the error.

ERRORS

     sched_getattr()  and  sched_setattr()  can  both fail for the following
     reasons:
     EINVAL attr is NULL; or pid is negative; or flags is not zero.
     ESRCH  The thread whose ID is pid could not be found.
     In addition, sched_getattr() can fail for the following reasons:
     E2BIG  The buffer specified by size and attr is too small.
     EINVAL size is invalid; that is, it is smaller than the initial version
            of the sched_attr structure (48 bytes) or larger than the system
            page size.
     In addition, sched_setattr() can fail for the following reasons:
     E2BIG  The buffer specified by size and attr is larger than the  kernel
            structure, and one or more of the excess bytes is nonzero.
     EBUSY  SCHED_DEADLINE admission control failure, see sched(7).
     EINVAL attr.sched_policy   is  not  one  of  the  recognized  policies;
            attr.sched_flags     contains     a     flag     other      than
            SCHED_FLAG_RESET_ON_FORK;  or attr.sched_priority is invalid; or
            attr.sched_policy is SCHED_DEADLINE and the deadline  scheduling
            parameters in attr are invalid.
     EPERM  The caller does not have appropriate privileges.
     EPERM  The  CPU  affinity  mask of the thread specified by pid does not
            include all CPUs in the system (see sched_setaffinity(2)).

VERSIONS

     These system calls first appeared in Linux 3.14.

CONFORMING TO

     These system calls are nonstandard Linux extensions.

NOTES

     sched_setattr()  provides  a   superset   of   the   functionality   of
     sched_setscheduler(2),  sched_setparam(2), nice(2), and (other than the
     ability to set the priority of all processes belonging to  a  specified
     user  or  all  processes  in a specified group) setpriority(2).  Analo-
     gously, sched_getattr() provides a superset  of  the  functionality  of
     sched_getscheduler(2),  sched_getparam(2),  and  (partially)  getprior-
     ity(2).

BUGS

     In Linux versions up to 3.15, sched_settattr() failed  with  the  error
     EFAULT instead of E2BIG for the case described in ERRORS.

SEE ALSO

     chrt(1), nice(2), sched_get_priority_max(2), sched_get_priority_min(2),
     sched_getaffinity(2), sched_getparam(2), sched_getscheduler(2),
     sched_rr_get_interval(2), sched_setaffinity(2), sched_setparam(2),
     sched_setscheduler(2), sched_yield(2), setpriority(2),
     pthread_getschedparam(3), pthread_setschedparam(3),
     pthread_setschedprio(3), capabilities(7), cpuset(7), sched(7)

COLOPHON

     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 SCHED_SETATTR(2)

/data/webs/external/dokuwiki/data/pages/man/sched_getattr.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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