sched_get_priority_max(2)

1sched_get_priority_max(2)     System Calls Manual    sched_get_priority_max(2)
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NAME

6       sched_get_priority_max,  sched_get_priority_min   - get static priority
7       range
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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

13       #include <sched.h>
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15       int sched_get_priority_max(int policy);
16       int sched_get_priority_min(int policy);
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DESCRIPTION

19       sched_get_priority_max() returns the maximum priority value that can be
20       used    with   the   scheduling   algorithm   identified   by   policy.
21       sched_get_priority_min() returns the minimum priority value that can be
22       used  with  the  scheduling  algorithm identified by policy.  Supported
23       policy  values  are  SCHED_FIFO,  SCHED_RR,  SCHED_OTHER,  SCHED_BATCH,
24       SCHED_IDLE,  and  SCHED_DEADLINE.  Further details about these policies
25       can be found in sched(7).
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27       Processes with numerically higher priority values are scheduled  before
28       processes  with numerically lower priority values.  Thus, the value re‐
29       turned by sched_get_priority_max() will be greater than the  value  re‐
30       turned by sched_get_priority_min().
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32       Linux  allows  the static priority range 1 to 99 for the SCHED_FIFO and
33       SCHED_RR policies, and the  priority  0  for  the  remaining  policies.
34       Scheduling priority ranges for the various policies are not alterable.
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36       The  range  of  scheduling  priorities may vary on other POSIX systems,
37       thus it is a good idea for portable applications to use a virtual  pri‐
38       ority  range  and  map  it  to  the  interval given by sched_get_prior‐
39       ity_max() and sched_get_priority_min() POSIX.1 requires a spread of  at
40       least  32 between the maximum and the minimum values for SCHED_FIFO and
41       SCHED_RR.
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43       POSIX systems on which  sched_get_priority_max()  and  sched_get_prior‐
44       ity_min()    are   available   define   _POSIX_PRIORITY_SCHEDULING   in
45       <unistd.h>.
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RETURN VALUE

48       On success, sched_get_priority_max() and  sched_get_priority_min()  re‐
49       turn  the  maximum/minimum priority value for the named scheduling pol‐
50       icy.  On error, -1 is returned, and errno is set to indicate the error.
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ERRORS

53       EINVAL The argument policy does not identify a defined scheduling  pol‐
54              icy.
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STANDARDS

57       POSIX.1-2008.
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HISTORY

60       POSIX.1-2001.
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