mirror of https://github.com/mkerrisk/man-pages
Remove crufty statement that this system call is not implemented.
The nice interval can be used to control the size of the round-robin quantum.
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@ -27,9 +27,9 @@
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.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
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.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
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.\" revision
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.\" revision
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.\"
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.\"
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.TH RR_GET_INTERVAL 2 1996-04-10 "Linux 1.3.81" "Linux Programmer's Manual"
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.TH SCHED_RR_GET_INTERVAL 2 2007-04-06 "Linux 2.6.19" "Linux Programmer's Manual"
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.SH NAME
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.SH NAME
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sched_rr_get_interval \- get the SCHED_RR interval for the named process
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sched_rr_get_interval \- get the SCHED_RR interval for the named process
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.SH SYNOPSIS
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.SH SYNOPSIS
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.B #include <sched.h>
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.B #include <sched.h>
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.sp
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.sp
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@ -37,16 +37,18 @@ sched_rr_get_interval \- get the SCHED_RR interval for the named process
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.SH DESCRIPTION
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.SH DESCRIPTION
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.BR sched_rr_get_interval ()
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.BR sched_rr_get_interval ()
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writes into the \fItimespec\fR structure pointed to by \fItp\fR the
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writes into the \fItimespec\fR structure pointed to by \fItp\fR the
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round robin time quantum for the process identified by \fIpid\fR.
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round-robin time quantum for the process identified by \fIpid\fR.
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The \fItimespec\fR structure has the following form:
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The \fItimespec\fR structure has the following form:
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.in +0.5i
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.nf
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.nf
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struct timespec {
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struct timespec {
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time_t tv_sec; /* seconds */
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time_t tv_sec; /* seconds */
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long tv_nsec; /* nanoseconds */
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long tv_nsec; /* nanoseconds */
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};
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};
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.fi
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.fi
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.in
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If
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If
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\fIpid\fR is zero, the time quantum for the calling process is written
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\fIpid\fR is zero, the time quantum for the calling process is written
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@ -54,9 +56,9 @@ into *\fItp\fR. The identified process should be running under the
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.I SCHED_RR
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.I SCHED_RR
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scheduling policy.
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scheduling policy.
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The round robin time quantum value is not alterable under Linux
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.\" The round-robin time quantum value is not alterable under Linux
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1.3.81.
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.\" 1.3.81.
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.\"
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POSIX systems on which
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POSIX systems on which
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.BR sched_rr_get_interval ()
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.BR sched_rr_get_interval ()
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is available define
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is available define
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@ -78,16 +80,27 @@ Problem with copying information to userspace.
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Invalid pid.
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Invalid pid.
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.TP
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.TP
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.B ENOSYS
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.B ENOSYS
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The system call is not yet implemented.
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The system call is not yet implemented (only on rather old kernels).
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.TP
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.TP
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.B ESRCH
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.B ESRCH
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The process whose ID is \fIpid\fR could not be found.
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The process whose ID is \fIpid\fR could not be found.
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.SH "CONFORMING TO"
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.SH "CONFORMING TO"
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POSIX.1-2001.
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POSIX.1-2001.
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.SH BUGS
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.SH "LINUX NOTES"
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As of Linux 1.3.81 \fBsched_rr_get_interval\fR() returns with error
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POSIX does not specify any mechanism for controlling the size of the
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ENOSYS, because SCHED_RR has not yet been fully implemented and tested
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round-robin time quantum.
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properly.
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However, Linux provides a (non-portable) method of doing this.
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The quantum can be controlled by adjusting the process's nice value (see
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.BR setpriority (2)).
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Assigning a negative (i.e., high) nice value results in a longer quantum;
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assigning a positive (i.e., low) nice value results in a shorter quantum.
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The default quantum is 0.1 seconds;
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the degree to which changing the nice value affects the
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quantum has varied somewhat across kernel versions.
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.\" .SH BUGS
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.\" As of Linux 1.3.81 \fBsched_rr_get_interval\fR() returns with error
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.\" ENOSYS, because SCHED_RR has not yet been fully implemented and tested
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.\" properly.
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.SH "SEE ALSO"
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.SH "SEE ALSO"
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.BR sched_setscheduler (2)
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.BR sched_setscheduler (2)
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has a description of the Linux scheduling scheme.
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has a description of the Linux scheduling scheme.
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