199 lines
4.2 KiB
HTML
199 lines
4.2 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SCHED_RR_GET_INTERVAL</TITLE>
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<H1>SCHED_RR_GET_INTERVAL</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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sched_rr_get_interval - get the SCHED_RR interval for the named process
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sched.h">sched.h</A>></B>
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<P>
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<B>int sched_rr_get_interval(pid_t </B><I>pid</I><B>, struct timespec *</B><I>tp</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>sched_rr_get_interval</B>()
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writes into the
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<I>timespec</I>
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structure pointed to by
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<I>tp</I>
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the round-robin time quantum for the process identified by
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<I>pid</I>.
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The specified process should be running under the
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<B>SCHED_RR</B>
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scheduling policy.
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<P>
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The
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<I>timespec</I>
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structure has the following form:
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<P>
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struct timespec {
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<BR> time_t tv_sec; /* seconds */
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<BR> long tv_nsec; /* nanoseconds */
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};
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<P>
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If
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<I>pid</I>
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is zero, the time quantum for the calling process is written into
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<I>*tp</I>.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success,
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<B>sched_rr_get_interval</B>()
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returns 0.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="1"><B>EFAULT</B>
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<DD>
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Problem with copying information to user space.
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<DT id="2"><B>EINVAL</B>
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<DD>
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Invalid pid.
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<DT id="3"><B>ENOSYS</B>
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<DD>
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The system call is not yet implemented (only on rather old kernels).
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<DT id="4"><B>ESRCH</B>
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<DD>
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Could not find a process with the ID
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<I>pid</I>.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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POSIX systems on which
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<B>sched_rr_get_interval</B>()
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is available define
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<B>_POSIX_PRIORITY_SCHEDULING</B>
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in
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<I><<A HREF="file:///usr/include/unistd.h">unistd.h</A>></I>.
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<A NAME="lbAI"> </A>
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<H3>Linux notes</H3>
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POSIX does not specify any mechanism for controlling the size of the
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round-robin time quantum.
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Older Linux kernels provide a (nonportable) 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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<B><A HREF="/cgi-bin/man/man2html?2+setpriority">setpriority</A></B>(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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This method of adjusting the quantum was removed
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starting with Linux 2.6.24.
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<P>
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Linux 3.9 added
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a new mechanism for adjusting (and viewing) the
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<B>SCHED_RR</B>
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quantum: the
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<I>/proc/sys/kernel/sched_rr_timeslice_ms</I>
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file exposes the quantum as a millisecond value, whose default is 100.
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Writing 0 to this file resets the quantum to the default value.
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<A NAME="lbAJ"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7)
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<A NAME="lbAK"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="9"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="10"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="11"><A HREF="#lbAH">NOTES</A><DD>
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<DL>
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<DT id="12"><A HREF="#lbAI">Linux notes</A><DD>
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</DL>
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<DT id="13"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="14"><A HREF="#lbAK">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:34 GMT, March 31, 2021
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