man2/sched_get_priority_max.2

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   3 .\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
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  25 .\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
  26 .\"            First version written
  27 .\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
  28 .\"            revision
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  30 .TH GET_PRIORITY_MAX 2 1996-04-10 "Linux 1.3.81" "Linux Programmer's Manual"
  31 .SH NAME
  32 sched_get_priority_max, sched_get_priority_min  \- get static priority range
  33 .SH SYNOPSIS
  34 .B #include <sched.h>
  35 .sp
  36 \fBint sched_get_priority_max(int \fIpolicy\fB);
  37 .sp
  38 \fBint sched_get_priority_min(int \fIpolicy\fB);
  39 .fi
  40 .SH DESCRIPTION
  41 .B sched_get_priority_max
  42 returns the maximum priority value that can be used with the
  43 scheduling algorithm identified by \fIpolicy\fR.
  44 .B sched_get_priority_min
  45 returns the minimum priority value that can be used with the
  46 scheduling algorithm identified by \fIpolicy\fR. Supported \fIpolicy\fR
  47 values are
  48 .IR SCHED_FIFO ,
  49 .IR SCHED_RR ,
  50 and
  51 .IR SCHED_OTHER .
  52
  53 Processes with numerically higher priority values are scheduled before
  54 processes with numerically lower priority values. Thus, the value
  55 returned by \fBsched_get_priority_max\fR will be greater than the
  56 value returned by \fBsched_get_priority_min\fR.
  57
  58 Linux allows the static priority value range 1 to 99 for
  59 \fISCHED_FIFO\fR and \fISCHED_RR\fR and the priority 0 for
  60 \fISCHED_OTHER\fR. Scheduling priority ranges for the various policies
  61 are not alterable.
  62
  63 The range of scheduling priorities may vary on other POSIX systems,
  64 thus it is a good idea for portable applications to use a virtual
  65 priority range and map it to the interval given by
  66 \fBsched_get_priority_max\fR and \fBsched_get_priority_min\fR.
  67 POSIX.1b requires a spread of at least 32 between the maximum and the
  68 minimum values for \fISCHED_FIFO\fR and \fISCHED_RR\fR.
  69
  70 POSIX systems on which
  71 .B sched_get_priority_max
  72 and
  73 .B sched_get_priority_min
  74 are available define
  75 .I _POSIX_PRIORITY_SCHEDULING
  76 in <unistd.h>.
  77
  78 .SH "RETURN VALUE"
  79 On success,
  80 .B sched_get_priority_max
  81 and
  82 .B sched_get_priority_min
  83 return the maximum/minimum priority value for the named scheduling
  84 policy.
  85 On error, \-1 is returned,
  86 .I errno
  87 is set appropriately.
  88 .SH ERRORS
  89 .TP
  90 .B EINVAL
  91 The parameter \fIpolicy\fR does not identify a defined scheduling policy.
  92 .SH "CONFORMING TO"
  93 POSIX.1b (formerly POSIX.4)
  94 .SH "SEE ALSO"
  95 .BR sched_getaffinity (2),
  96 .BR sched_getparam (2),
  97 .BR sched_getscheduler (2),
  98 .BR sched_setaffinity (2),
  99 .BR sched_setparam (2),
 100 .BR sched_setscheduler (2)
 101 .PP
 102 .BR sched_setscheduler (2)
 103 has a description of the Linux scheduling scheme.
 104 .PP
 105 .I Programming for the real world \- POSIX.4
 106 by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0
 107 .br
 108 .I IEEE Std 1003.1b-1993
 109 (POSIX.1b standard)
 110 .br
 111 .I ISO/IEC 9945-1:1996