e72380dd09
and this manpage is somewhat machine independent. - Don't redundantly say that SMP support is present for all supported architectures. Instead, say that it is present for all Tier-1 architectures. - Note that an SMP kernel not booting on a UP machine is an i386-only exception. - Add a paragraph about hyperthreading support including some docco on the machdep.hlt_logical_cpus sysctl ps@ recently added. - Note that SMP support for alpha, ia64, and sparc64 debuted in 5.0.
98 lines
3.3 KiB
Groff
98 lines
3.3 KiB
Groff
.\" Copyright (c) 1997
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.\" Steve Passe <fsmp@FreeBSD.ORG>. 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. The name of the developer may NOT be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 December 5, 2002
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.Dt SMP 4
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.Os
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.Sh NAME
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.Nm SMP
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.Nd description of the FreeBSD Symmetric MultiProcessor kernel
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.Sh SYNOPSIS
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.Cd options SMP
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.Sh DESCRIPTION
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The
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.Nm
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kernel implements symmetric multiprocessor support.
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.Sh COMPATIBILITY
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Support for multi-processor systems is present for all Tier-1
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architectures on
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.Fx .
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Currently, this includes alpha, i386, ia64, and sparc64.
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Support is enabled using
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.Cd options SMP .
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On most platforms it is permissible to use the SMP
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kernel configuration on non-SMP equipped motherboards.
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The only exception to this rule is the i386 platform.
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.Pp
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For i386 systems, the
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.Nm
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kernel supports motherboards that follow the Intel MP specification,
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version 1.4.
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In addition to
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.Cd options SMP ,
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i386 also requires
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.Cd options APIC_IO .
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The
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.Xr mptable 1
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command may be used to view the status of multi-processor support.
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.Pp
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.Fx
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supports hyperthreading on Intel CPU's on the i386 platform.
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By default, logical CPUs are not used to execute user processes due to
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performance penalties under common loads.
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To allow the logical CPUs to execute user processes,
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turn off the
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.Va machdep.hlt_logical_cpus
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sysctl by setting its value to zero.
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.Sh SEE ALSO
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.Xr mptable 1 ,
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.Xr condvar 9 ,
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.Xr msleep 9 ,
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.Xr mtx_pool 9 ,
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.Xr mutex 9 ,
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.Xr sema 9 ,
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.Xr sx 9
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.Sh HISTORY
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The
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.Nm
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kernel's early history is not (properly) recorded. It was developed
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in a separate CVS branch until April 26, 1997, at which point it was
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merged into 3.0-current. By this date 3.0-current had already been
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merged with Lite2 kernel code.
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.Pp
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.Fx 5.0
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introduced support for a host of new synchronization primitives, and
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a move towards fine-grained kernel locking rather than reliance on
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a Giant kernel lock.
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The SMPng Project relied heavily on the support of BSDi, who provided
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reference source code from the fine-grained SMP implementation found
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in
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.Bsx .
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.Pp
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.Fx 5.0
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also introduced support for SMP on the alpha, ia64, and sparc64 architectures.
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.Sh AUTHORS
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.An Steve Passe Aq fsmp@FreeBSD.org
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