2005-04-07 21:57:19 +00:00
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.\" Copyright (c) 2005 Robert N. M. Watson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 7, 2005
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.Os
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.Dt SCHED_4BSD 4
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.Sh NAME
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.Nm sched_4bsd
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2005-06-16 18:46:17 +00:00
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.Nd "4.4BSD scheduler"
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2005-04-07 21:57:19 +00:00
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.Sh SYNOPSIS
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.Cd "options SCHED_4BSD"
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.Sh DESCRIPTION
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2005-06-16 18:46:17 +00:00
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The
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2005-04-07 21:57:19 +00:00
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.Nm
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2005-06-16 18:46:17 +00:00
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scheduler
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2005-04-07 21:57:19 +00:00
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is the default system scheduler, providing both high throughput and solid
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interactive response in the presence of load.
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.Pp
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The following sysctls are relevant to the operation of
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.Nm :
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.Bl -tag -width indent
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2005-06-16 18:46:17 +00:00
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.It Va kern.sched.name
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2005-04-07 21:57:19 +00:00
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This read-only sysctl reports the name of the active scheduler.
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2005-06-16 18:46:17 +00:00
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.It Va kern.sched.quantum
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2005-04-07 21:57:19 +00:00
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This read-write sysctl reports or sets the length of the quantum (in
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micro-seconds) granted to a thread.
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2005-06-16 18:46:17 +00:00
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.It Va kern.sched.ipiwakeup.enabled
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2005-04-07 21:57:19 +00:00
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This read-write sysctl sets whether or not the scheduler will generate an
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inter-processor interrupt (IPI) to an idle CPU when a thread is woken up.
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Otherwise, idle CPUs will wait until the next clock tick before looking for
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new work.
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2005-06-16 18:46:17 +00:00
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.It Va kern.sched.preemption
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2005-04-07 21:57:19 +00:00
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This read-only sysctl reports whether or not the kernel is configured to
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support preemption, which reduces the latency to run lower priority threads
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on wakeup.
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.El
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.Pp
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Some sysctls will be available only on systems supporting SMP.
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.Sh SEE ALSO
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2006-06-14 02:16:51 +00:00
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.Xr sched_core 4 ,
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2005-04-07 21:57:19 +00:00
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.Xr sched_ule 4 ,
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.Xr sysctl 8
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.Sh HISTORY
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The
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.Nm
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scheduler has been present, in various forms, since the inception of
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.Bx .
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.Sh BUGS
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While a highly robust and time-tested scheduler,
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.Nm
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2005-04-09 08:47:38 +00:00
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lacks specific knowledge of how to schedule advantageously in non-symmetric
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2005-04-07 21:57:19 +00:00
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processor configurations, such as hyper-threading.
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