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[linuxjm/jm.git] / manual / LDP_man-pages / draft / man2 / ioprio_set.2

.\" This is _*_ nroff _*_ source. Emacs, gimme all those colors :)
.\"
.\" Copyright (c) International Business Machines orp., 2006
.\"
.\" This program is free software; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
.\" the GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with this program; if not, write to the Free Software
.\" Foundation, Inc., 59 Temple Place, Suite 330, Boston,
.\" MA 02111-1307 USA
.\"
.\" HISTORY:
.\" 2006-04-27, created by Eduardo M. Fleury <efleury@br.ibm.com>
.\" with various additions by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" Japanese Version Copyright (c) 2007 Akihiro MOTOKI
.\"         all rights reserved.
.\" Translated 2007-01-09, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v2.43
.\" Updated 2008-08-06, Akihiro MOTOKI, LDP v3.05
.\"
.TH IOPRIO_SET 2 2008-07-09 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O ioprio_get, ioprio_set \- get/set I/O scheduling class and priority
ioprio_get, ioprio_set \- I/O ¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤ÈÍ¥ÀèÅÙ¤ÎÀßÄê/¼èÆÀ
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.BI "int ioprio_get(int " which ", int " who );
.BI "int ioprio_set(int " which ", int " who ", int " ioprio );
.fi
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The
.\"O .BR ioprio_get ()
.\"O and
.\"O .BR ioprio_set ()
.\"O system calls respectively get and set the I/O scheduling class and
.\"O priority of one or more processes.
¥·¥¹¥Æ¥à¥³¡¼¥ë
.BR ioprio_get ()
/
.BR ioprio_set ()
¤Ï¡¢(1¤Ä°Ê¾å¤Î) ¥×¥í¥»¥¹¤Î I/O ¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤È
Í¥ÀèÅ٤μèÆÀ/ÀßÄê¤ò¹Ô¤¦¡£

.\"O The
.\"O .I which
.\"O and
.\"O .I who
.\"O arguments identify the process(es) on which the system
.\"O calls operate.
.\"O The
.\"O .I which
.\"O argument determines how
.\"O .I who
.\"O is interpreted, and has one of the following values:
.I which
¤È
.I who
°ú¤­¿ô¤Ç¥·¥¹¥Æ¥à¥³¡¼¥ë¤ÎÁàºîÂоݤȤʤë¥×¥í¥»¥¹¤ò»Ø¼¨¤¹¤ë¡£
.I which
°ú¤­¿ô¤Ï¡¢
.I who
¤ò¤É¤Î¤è¤¦¤Ë²ò¼á¤¹¤ë¤«¤ò·è¤á¤ë¤â¤Î¤Ç¡¢°Ê²¼¤Î¤¤¤º¤ì¤«°ì¤Ä¤ò»ØÄꤹ¤ë¡£
.TP
.B IOPRIO_WHO_PROCESS
.\"O .I who
.\"O is a process ID identifying a single process.
.I who
¤Ï¥×¥í¥»¥¹ID ¤Ç¤¢¤ê¡¢»ØÄꤵ¤ì¤¿ 1 ¥×¥í¥»¥¹¤¬ÂоݤȤʤ롣
.TP
.B IOPRIO_WHO_PGRP
.\"O .I who
.\"O is a process group ID identifying all the members of a process group.
.I who
¤Ï¥×¥í¥»¥¹¥°¥ë¡¼¥×ID ¤Ç¤¢¤ê¡¢¥×¥í¥»¥¹¥°¥ë¡¼¥×¤ÎÁ´¥á¥ó¥Ð¤¬ÂоݤȤʤ롣
.TP
.B IOPRIO_WHO_USER
.\"O .I who
.\"O is a user ID identifying all of the processes that
.\"O have a matching real UID.
.I who
¤Ï¥æ¡¼¥¶ID ¤Ç¤¢¤ê¡¢¼Â UID ¤Ë°ìÃפ¹¤ëÁ´¥×¥í¥»¥¹¤¬ÂоݤȤʤ롣
.PP
.\"O If
.\"O .I which
.\"O is specified as
.\"O .B IOPRIO_WHO_PGRP
.\"O or
.\"O .B IOPRIO_WHO_USER
.\"O when calling
.\"O .BR ioprio_get (),
.\"O and more than one process matches
.\"O .IR who ,
.\"O then the returned priority will be the highest one found among
.\"O all of the matching processes.
.\"O One priority is said to be
.\"O higher than another one if it belongs to a higher priority
.\"O class
.\"O .RB ( IOPRIO_CLASS_RT
.\"O is the highest priority class;
.\"O .B IOPRIO_CLASS_IDLE
.\"O is the lowest)
.\"O or if it belongs to the same priority class as the other process but
.\"O has a higher priority level (a lower priority number means a
.\"O higher priority level).
.BR ioprio_get ()
¤Î¸Æ¤Ó½Ð¤·»þ¤Ë
.I which
¤Ë
.B IOPRIO_WHO_PGRP
¤«
.B IOPRIO_WHO_USER
¤¬»ØÄꤵ¤ì¡¢
.I who
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Í¥ÀèÅÙ¤¬¹â¤¤¤È¤Ï¡¢¤è¤ê¹â¤¤Í¥ÀèÅÙ¥¯¥é¥¹¤Ë°¤·¤Æ¤¤¤ë
.RB ( IOPRIO_CLASS_RT
¤¬ºÇ¤â¹â¤¤Í¥ÀèÅÙ¥¯¥é¥¹¤Ç¡¢
.B IOPRIO_CLASS_IDLE
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(Í¥ÀèÅÙÈֹ椬¾®¤µ¤¤Êý¤¬Í¥ÀèÅÙ¥ì¥Ù¥ë¤¬¹â¤¤¤³¤È¤ò°ÕÌ£¤¹¤ë)¡¢
¤È¤¤¤¦¤³¤È¤Ç¤¢¤ë¡£

.\"O The
.\"O .I ioprio
.\"O argument given to
.\"O .BR ioprio_set ()
.\"O is a bit mask that specifies both the scheduling class and the
.\"O priority to be assigned to the target process(es).
.\"O The following macros are used for assembling and dissecting
.\"O .I ioprio
.\"O values:
.BR ioprio_set ()
¤ËÅϤ¹
.I ioprio
°ú¤­¿ô¤Ï¡¢ÂоݤȤʤë¥×¥í¥»¥¹¤Ë³ä¤êÅö¤Æ¤ë¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤È
Í¥ÀèÅÙ¤ÎξÊý¤ò»ØÄꤹ¤ë¥Ó¥Ã¥È¥Þ¥¹¥¯¤Ç¤¢¤ë¡£
.I ioprio
¤ÎÃͤòÁȤßΩ¤Æ¤¿¤ê²ò¼á¤¹¤ë¤Î¤Ë¡¢°Ê²¼¤Î¥Þ¥¯¥í¤¬ÍøÍѤǤ­¤ë¡£
.TP
.BI IOPRIO_PRIO_VALUE( class ", " data )
.\"O Given a scheduling
.\"O .I class
.\"O and priority
.\"O .RI ( data ),
.\"O this macro combines the two values to produce an
.\"O .I ioprio
.\"O value, which is returned as the result of the macro.
¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹
.I class
¤ÈÍ¥ÀèÅÙ
.RI ( data )
¤òÍ¿¤¨¤ë¤È¡¢¤³¤Î¥Þ¥¯¥í¤Ï 2¤Ä¤ÎÃͤòÁȤ߹ç¤ï¤»¤Æ¡¢
.I ioprio
ÃͤòÀ¸À®¤·¡¢¥Þ¥¯¥í¤Î·ë²Ì¤È¤·¤ÆÊÖ¤¹¡£
.TP
.BI IOPRIO_PRIO_CLASS( mask )
.\"O Given
.\"O .I mask
.\"O (an
.\"O .I ioprio
.\"O value), this macro returns its I/O class component, that is,
.\"O one of the values
.\"O .BR IOPRIO_CLASS_RT ,
.\"O .BR IOPRIO_CLASS_BE ,
.\"O or
.\"O .BR IOPRIO_CLASS_IDLE .
.I mask
.RI ( ioprio
ÃÍ) ¤òÍ¿¤¨¤ë¤È¡¢¤³¤Î¥Þ¥¯¥í¤Ï I/O ¥¯¥é¥¹Í×ÁÇ¡¢¤Ä¤Þ¤ê
.BR IOPRIO_CLASS_RT ,
.BR IOPRIO_CLASS_BE ,
.B IOPRIO_CLASS_IDLE
¤Î¤¤¤º¤ì¤«°ì¤Ä¤ÎÃͤòÊÖ¤¹¡£
.TP
.BI IOPRIO_PRIO_DATA( mask )
.\"O Given
.\"O .I mask
.\"O (an
.\"O .I ioprio
.\"O value), this macro returns its priority
.\"O .RI ( data )
.\"O component.
.I mask
.RI ( ioprio
ÃÍ) ¤òÍ¿¤¨¤ë¤È¡¢¤³¤Î¥Þ¥¯¥í¤ÏÍ¥ÀèÅÙ
.RI ( data )
Í×ÁǤòÊÖ¤¹¡£
.PP
.\"O See the NOTES section for more
.\"O information on scheduling classes and priorities.
¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤ÈÍ¥ÀèÅ٤˴ؤ¹¤ë¾Ü¤·¤¤¾ðÊó¤Ï¡¢
¡ÖÈ÷¹Í¡×¤ÎÀá¤ò»²¾È¤Î¤³¤È¡£

.\"O I/O priorities are supported for reads and for synchronous
.\"O .RB ( O_DIRECT ,
.\"O .BR O_SYNC )
.\"O writes.
.\"O I/O priorities are not supported for asynchronous
.\"O writes because they are issued outside the context of the program
.\"O dirtying the memory, and thus program-specific priorities do not apply.
I/O Í¥ÀèÅÙ¤ÏÆɤ߽Ф·¤ÈƱ´ü½ñ¤­¹þ¤ß
.RB ( O_DIRECT ,
.BR O_SYNC )
¤ËÂбþ¤·¤Æ¤¤¤ë¡£
I/O Í¥ÀèÅÙ¤ÏÈóƱ´ü½ñ¤­¹þ¤ß¤Ë¤ÏÂбþ¤·¤Æ¤¤¤Ê¤¤¡£¤Ê¤¼¤Ê¤é¡¢
ÈóƱ´ü½ñ¤­¹þ¤ß¤Ï¥á¥â¥ê½ñ¤­´¹¤¨¤ò¹Ô¤¦¥×¥í¥°¥é¥à¤ÎÆ°ºî (context) ¤È¤Ï
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¤Ç¤¢¤ë¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O On success,
.\"O .BR ioprio_get ()
.\"O returns the
.\"O .I ioprio
.\"O value of the process with highest I/O priority of any of the processes
.\"O that match the criteria specified in
.\"O .I which
.\"O and
.\"O .IR who .
.\"O On error, \-1 is returned, and
.\"O .I errno
.\"O is set to indicate the error.
À®¸ù¤¹¤ë¤È¡¢
.BR ioprio_get ()
¤Ï¡¢
.I which
¤È
.I who
¤Ç»ØÄꤵ¤ì¤¿´ð½à¤Ë¹çÃפ·¤¿Á´¥×¥í¥»¥¹¤ÇºÇ¤â¹â¤¤ I/O Í¥ÀèÅÙ¤ò»ý¤Ä¥×¥í¥»¥¹¤Î
.I ioprio
ÃͤòÊÖ¤¹¡£
¥¨¥é¡¼¤Î¾ì¹ç¡¢\-1 ¤òÊÖ¤·¡¢
.I errno
¤Ë¥¨¥é¡¼¤ò¼¨¤¹ÃͤòÀßÄꤹ¤ë¡£
.PP
.\"O On success,
.\"O .BR ioprio_set ()
.\"O returns 0.
.\"O On error, \-1 is returned, and
.\"O .I errno
.\"O is set to indicate the error.
À®¸ù¤¹¤ë¤È¡¢
.BR ioprio_set ()
¤Ï 0 ¤òÊÖ¤¹¡£
¥¨¥é¡¼¤Î¾ì¹ç¡¢\-1 ¤òÊÖ¤·¡¢
.I errno
¤Ë¥¨¥é¡¼¤ò¼¨¤¹ÃͤòÀßÄꤹ¤ë¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.TP
.B EINVAL
.\"O Invalid value for
.\"O .I which
.\"O or
.\"O .IR ioprio .
.\"O Refer to the NOTES section for available scheduler
.\"O classes and priority levels for
.\"O .IR ioprio .
.I which
¤«
.I ioprio
¤ÎÃͤ¬ÉÔÀµ¤Ç¤¢¤ë¡£
.I ioprio
ÍѤ˻ØÄê²Äǽ¤Ê¥¹¥±¥¸¥å¡¼¥é¥¯¥é¥¹¤ÈÍ¥ÀèÅÙ¥ì¥Ù¥ë¤Ë¤Ä¤¤¤Æ¤Ï
¡ÖÈ÷¹Í¡×¤ò»²¾È¤Î¤³¤È¡£
.TP
.B EPERM
.\"O The calling process does not have the privilege needed to assign this
.\"O .I ioprio
.\"O to the specified process(es).
.\"O See the NOTES section for more information on required
.\"O privileges for
.\"O .BR ioprio_set ().
¸Æ¤Ó½Ð¤·¸µ¥×¥í¥»¥¹¤¬¡¢»ØÄꤵ¤ì¤¿¥×¥í¥»¥¹¤Ë
.I ioprio
¤ò³ä¤êÅö¤Æ¤ë¤Î¤ËɬÍפʸ¢¸Â¤ò»ý¤Ã¤Æ¤¤¤Ê¤¤¡£
.BR ioprio_set ()
¤ËɬÍפʸ¢¸Â¤Ë¤Ä¤¤¤Æ¤Î¾Ü¤·¤¤¾ðÊó¤Ï¡ÖÈ÷¹Í¡×¤ÎÀá¤ò»²¾È¤Î¤³¤È¡£
.TP
.B ESRCH
.\"O No process(es) could be found that matched the specification in
.\"O .I which
.\"O and
.\"O .IR who .
.I which
¤È
.I who
¤Ç»ØÄꤵ¤ì¤¿´ð½à¤Ë¹çÃפ¹¤ë¥×¥í¥»¥¹¤¬¸«¤Ä¤«¤é¤Ê¤«¤Ã¤¿¡£
.\"O .SH VERSIONS
.SH ¥Ð¡¼¥¸¥ç¥ó
.\"O These system calls have been available on Linux since
.\"O kernel 2.6.13.
¤³¤ì¤é¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï¥«¡¼¥Í¥ë 2.6.13 °Ê¹ß¤Î Linux ¤ÇÍøÍѲÄǽ¤Ç¤¢¤ë¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
.\"O These system calls are Linux-specific.
¤³¤ì¤é¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï Linux Æȼ«¤Ç¤¢¤ë¡£
.\"O .SH NOTES
.SH È÷¹Í
.\"O Glibc does not provide wrapper for these system calls; call them using
.\"O .BR syscall (2).
glibc ¤Ï¤³¤ì¤é¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤ËÂФ¹¤ë¥é¥Ã¥Ñ¡¼´Ø¿ô¤òÄ󶡤·¤Æ¤¤¤Ê¤¤¡£
.BR syscall (2)
¤ò»È¤Ã¤Æ¸Æ¤Ó½Ð¤¹¤³¤È¡£

.\"O These system calls only have an effect when used
.\"O in conjunction with an I/O scheduler that supports I/O priorities.
.\"O As at kernel 2.6.17 the only such scheduler is the Completely Fair Queuing
.\"O (CFQ) I/O scheduler.
¤³¤ì¤é¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï¡¢I/O Í¥ÀèÅÙ¤ËÂбþ¤·¤¿ I/O ¥¹¥±¥¸¥å¡¼¥é¤È
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¥«¡¼¥Í¥ë 2.6.17 ¤Ç¤Ï¡¢¤³¤Î¾ò·ï¤òËþ¤¿¤¹¥¹¥±¥¸¥å¡¼¥é¤Ï
Completely Fair Queuing (CFQ) I/O ¥¹¥±¥¸¥å¡¼¥é¤À¤±¤Ç¤¢¤ë¡£
.\"O .SS "Selecting an I/O Scheduler"
.SS I/O ¥¹¥±¥¸¥å¡¼¥é¤ÎÁªÂò
.\"O I/O Schedulers are selected on a per-device basis via the special
.\"O file
.\"O .IR /sys/block/<device>/queue/scheduler .
I/O ¥¹¥±¥¸¥å¡¼¥é¤ÎÁªÂò¤Ï¥Ç¥Ð¥¤¥¹Ã±°Ì¤Ë¹Ô¤ï¤ì¡¢¤½¤ÎÁªÂò¤Ï
¥¹¥Ú¥·¥ã¥ë¥Õ¥¡¥¤¥ë
.I /sys/block/<device>/queue/scheduler
·Ðͳ¤Ç¹Ô¤ï¤ì¤ë¡£

.\"O One can view the current I/O scheduler via the
.\"O .I /sys
.\"O file system.
.\"O For example, the following command
.\"O displays a list of all schedulers currently loaded in the kernel:
¸½ºß¤Î I/O ¥¹¥±¥¸¥å¡¼¥é¤Ï
.I /sys
¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à·Ðͳ¤Ç»²¾È¤Ç¤­¤ë¡£Î㤨¤Ð¡¢°Ê²¼¤Î¥³¥Þ¥ó¥É¤ò¼Â¹Ô¤¹¤ë¤È¡¢
¸½ºß¥«¡¼¥Í¥ë¤Ç¥í¡¼¥É¤µ¤ì¤Æ¤¤¤ë¥¹¥±¥¸¥å¡¼¥é¤ÎÁ´¥ê¥¹¥È¤¬É½¼¨¤µ¤ì¤ë¡£
.sp
.RS
.nf
.RB "$" " cat /sys/block/hda/queue/scheduler"
noop anticipatory deadline [cfq]
.fi
.RE
.sp
.\"O The scheduler surrounded by brackets is the one actually
.\"O in use for the device
.\"O .RI ( hda
.\"O in the example).
³ç¸Ì¤Ç°Ï¤Þ¤ì¤¿¥¹¥±¥¸¥å¡¼¥é¤¬¤½¤Î¥Ç¥Ð¥¤¥¹ (¾å¤ÎÎã¤Ç¤Ï
.IR hda )
¤Ë¤Ä¤¤¤Æ¼ÂºÝ¤Ë»ÈÍѤµ¤ì¤Æ¤¤¤ë¥¹¥±¥¸¥å¡¼¥é¤Ç¤¢¤ë¡£
.\"O Setting another scheduler is done by writing the name of the
.\"O new scheduler to this file.
.\"O For example, the following command will set the
.\"O scheduler for the
.\"O .I hda
.\"O device to
.\"O .IR cfq :
Ê̤Υ¹¥±¥¸¥å¡¼¥é¤òÀßÄꤹ¤ë¤Ë¤Ï¡¢¤³¤Î¥Õ¥¡¥¤¥ë¤Ë¿·¤·¤¤¥¹¥±¥¸¥å¡¼¥é̾¤ò
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.I hda
¤Î¥¹¥±¥¸¥å¡¼¥é¤È¤·¤Æ
.I cfq
¤¬ÀßÄꤵ¤ì¤ë¡£
.sp
.RS
.nf
.RB "$" " su"
Password:
.RB "#" " echo cfq > /sys/block/hda/queue/scheduler"
.fi
.RE
.\"O .SS "The Completely Fair Queuing (CFQ) I/O Scheduler"
.SS "Completely Fair Queuing (CFQ) I/O ¥¹¥±¥¸¥å¡¼¥é"
.\"O Since v3 (aka CFQ Time Sliced) CFQ implements
.\"O I/O nice levels similar to those
.\"O of CPU scheduling.
.\"O These nice levels are grouped in three scheduling classes
.\"O each one containing one or more priority levels:
¥Ð¡¼¥¸¥ç¥ó 3 (ÊÌ̾ CFQ Time Sliced) °Ê¹ß¡¢
CPU ¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¤ÈƱÍͤΠI/O nice ¥ì¥Ù¥ë¤¬ CFQ ¤Ë¼ÂÁõ¤µ¤ì¤Æ¤¤¤ë¡£
¤³¤ì¤é¤Î nice ¥ì¥Ù¥ë¤Ï 3¤Ä¤Î¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤ËʬÎà¤Ç¤­¡¢
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.TP
.BR IOPRIO_CLASS_RT " (1)"
.\"O This is the real-time I/O class.
.\"O This scheduling class is given
.\"O higher priority than any other class:
.\"O processes from this class are
.\"O given first access to the disk every time.
.\"O Thus this I/O class needs to be used with some
.\"O care: one I/O real-time process can starve the entire system.
.\"O Within the real-time class,
.\"O there are 8 levels of class data (priority) that determine exactly
.\"O how much time this process needs the disk for on each service.
.\"O The highest real-time priority level is 0; the lowest is 7.
.\"O In the future this might change to be more directly mappable to
.\"O performance, by passing in a desired data rate instead.
¤³¤ì¤Ï¥ê¥¢¥ë¥¿¥¤¥à I/O ¥¯¥é¥¹¤Ç¤¢¤ë¡£
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³ä¤êÅö¤Æ¤é¤ì¤ë¡£¤½¤Î¤¿¤á¡¢¤³¤Î I/O ¥¯¥é¥¹¤ò»È¤¦ºÝ¤Ë¤Ï¡¢
¤¿¤Ã¤¿°ì¤Ä¤Î ¥ê¥¢¥ë¥¿¥¤¥à I/O ¥¯¥é¥¹¤Î¥×¥í¥»¥¹¤Ë¤è¤ê
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¤³¤ÎÃͤϡ¢¤½¤Î¥×¥í¥»¥¹¤¬ 1²ó¤Î¥Ç¥£¥¹¥¯¥¢¥¯¥»¥¹¤Ë¤É¤ì¤À¤±¤Î
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¤è¤êľÀÜŪ¤ËÀ­Ç½¾ò·ï¤òÈ¿±Ç¤Ç¤­¤ë¤è¤¦¤ËÊѹ¹¤µ¤ì¤ë¤«¤â¤·¤ì¤Ê¤¤¡£
.TP
.BR IOPRIO_CLASS_BE " (2)"
.\"O This is the best-effort scheduling class,
.\"O which is the default for any process
.\"O that hasn't set a specific I/O priority.
.\"O The class data (priority) determines how much
.\"O I/O bandwidth the process will get.
.\"O Best-effort priority levels are analogous to CPU nice values
.\"O (see
.\"O .BR getpriority (2)).
.\"O The priority level determines a priority relative
.\"O to other processes in the best-effort scheduling class.
.\"O Priority levels range from 0 (highest) to 7 (lowest).
¤³¤ì¤Ï ¥Ù¥¹¥È¥¨¥Õ¥©¡¼¥È¡¦¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¥¯¥é¥¹¤Ç¤¢¤ë¡£
¤³¤Î¥¯¥é¥¹¤Ï¡¢ÆÃÄê¤Î I/O Í¥ÀèÅÙ¤òÀßÄꤷ¤Æ¤¤¤Ê¤¤¥×¥í¥»¥¹¤Î
¥Ç¥Õ¥©¥ë¥ÈÃͤǤ¢¤ë¡£
class data (Í¥ÀèÅÙ¥ì¥Ù¥ë) ¤Ë¤è¤ê¡¢¤½¤Î¥×¥í¥»¥¹¤¬¤É¤ÎÄøÅÙ¤Î
I/O ÂÓ°è¤òÆÀ¤é¤ì¤ë¤«¤¬·èÄꤵ¤ì¤ë¡£
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.RB ( getpriority (2)
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.BR IOPRIO_CLASS_IDLE " (3)"
.\"O This is the idle scheduling class.
.\"O Processes running at this level only get I/O
.\"O time when no-one else needs the disk.
.\"O The idle class has no class data.
.\"O Attention is required when assigning this priority class to a process,
.\"O since it may become starved if higher priority processes are
.\"O constantly accessing the disk.
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.\"O Refer to
.\"O .I Documentation/block/ioprio.txt
.\"O for more information on the CFQ I/O Scheduler and an example program.
CFQ I/O ¥¹¥±¥¸¥å¡¼¥é¤Î¹¹¤Ê¤ë¾ðÊó¤È¥µ¥ó¥×¥ë¥×¥í¥°¥é¥à¤Ë¤Ä¤¤¤Æ¤Ï
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.\"O .SS "Required permissions to set I/O priorities"
.SS "I/O Í¥ÀèÅÙ¤ÎÀßÄê¤ËɬÍפʵö²Ä"
.\"O Permission to change a process's priority is granted or denied based
.\"O on two assertions:
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.\"O .B "Process ownership"
.B "¥×¥í¥»¥¹¤Î½êÍ­¸¢"
.\"O An unprivileged process may only set the I/O priority of a process
.\"O whose real UID
.\"O matches the real or effective UID of the calling process.
.\"O A process which has the
.\"O .B CAP_SYS_NICE
.\"O capability can change the priority of any process.
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.\"O .B "What is the desired priority"
.B "¤É¤ÎÍ¥ÀèÅÙ¤ËÀßÄꤷ¤è¤¦¤È¤·¤Æ¤¤¤ë¤«"
.\"O Attempts to set very high priorities
.\"O .RB ( IOPRIO_CLASS_RT )
.\"O require the
.\"O .B CAP_SYS_ADMIN
.\"O capability.
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.\"O Kernel versions up to 2.6.24 also required
.\"O .B CAP_SYS_ADMIN
.\"O to set a very low priority
.\"O .RB ( IOPRIO_CLASS_IDLE ),
.\"O but since Linux 2.6.25, this is no longer required.
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.\"O A call to
.\"O .BR ioprio_set ()
.\"O must follow both rules, or the call will fail with the error
.\"O .BR EPERM .
.BR ioprio_set ()
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.\"O .SH BUGS
.SH ¥Ð¥°
.\" 6 May 07: Bug report raised:
.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=4464
.\" Ulriich Drepper replied that he wasn't going to add these
.\" to glibc.
.\"O Glibc does not yet provide a suitable header file defining
.\"O the function prototypes and macros described on this page.
.\"O Suitable definitions can be found in
.\"O .IR linux/ioprio.h .
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.I linux/ioprio.h
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.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR getpriority (2),
.BR open (2),
.BR capabilities (7)
.sp
.\"O Documentation/block/ioprio.txt in the kernel source tree.
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