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1 | .\" Hey Emacs! This file is -*- nroff -*- source. |
| 2 | .\" | |
| 3 | .\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996 | |
| 4 | .\" | |
| 5 | .\" This is free documentation; you can redistribute it and/or | |
| 6 | .\" modify it under the terms of the GNU General Public License as | |
| 7 | .\" published by the Free Software Foundation; either version 2 of | |
| 8 | .\" the License, or (at your option) any later version. | |
| 9 | .\" | |
| 10 | .\" The GNU General Public License's references to "object code" | |
| 11 | .\" and "executables" are to be interpreted as the output of any | |
| 12 | .\" document formatting or typesetting system, including | |
| 13 | .\" intermediate and printed output. | |
| 14 | .\" | |
| 15 | .\" This manual is distributed in the hope that it will be useful, | |
| 16 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 17 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 18 | .\" GNU General Public License for more details. | |
| 19 | .\" | |
| 20 | .\" You should have received a copy of the GNU General Public | |
| 21 | .\" License along with this manual; if not, write to the Free | |
| 22 | .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, | |
| 23 | .\" USA. | |
| 24 | .\" | |
| 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 | |
| 29 | .\" | |
| 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 |