FreeBSD-5.3/share/man/man4/smp.4

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.\"	Steve Passe <fsmp@FreeBSD.ORG>.  All rights reserved.
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.\" $FreeBSD: src/share/man/man4/smp.4,v 1.19 2004/06/16 08:33:54 ru Exp $
.\"
.Dd December 5, 2002
.Dt SMP 4
.Os
.Sh NAME
.Nm SMP
.Nd description of the FreeBSD Symmetric MultiProcessor kernel
.Sh SYNOPSIS
.Cd options SMP
.Sh DESCRIPTION
The
.Nm
kernel implements symmetric multiprocessor support.
.Sh COMPATIBILITY
Support for multi-processor systems is present for all Tier-1
architectures on
.Fx .
Currently, this includes alpha, i386, ia64, and sparc64.
Support is enabled using
.Cd options SMP .
It is permissible to use the SMP kernel configuration on non-SMP equipped
motherboards.
.Sh I386 NOTES
For i386 systems, the
.Nm
kernel supports motherboards that follow the Intel MP specification,
version 1.4.
In addition to
.Cd options SMP ,
i386 also requires
.Cd device apic .
The
.Xr mptable 1
command may be used to view the status of multi-processor support.
.Pp
.Fx
supports hyperthreading on Intel CPU's on the i386 platform.
Since using logical CPUs can cause performance penalties under certain loads,
the logical CPUs can be disabled by setting the
.Va machdep.hlt_logical_cpus
sysctl to one.
.Sh SEE ALSO
.Xr mptable 1 ,
.Xr condvar 9 ,
.Xr msleep 9 ,
.Xr mtx_pool 9 ,
.Xr mutex 9 ,
.Xr sema 9 ,
.Xr sx 9
.Sh HISTORY
The
.Nm
kernel's early history is not (properly) recorded.
It was developed
in a separate CVS branch until April 26, 1997, at which point it was
merged into 3.0-current.
By this date 3.0-current had already been
merged with Lite2 kernel code.
.Pp
.Fx 5.0
introduced support for a host of new synchronization primitives, and
a move towards fine-grained kernel locking rather than reliance on
a Giant kernel lock.
The SMPng Project relied heavily on the support of BSDi, who provided
reference source code from the fine-grained SMP implementation found
in
.Bsx .
.Pp
.Fx 5.0
also introduced support for SMP on the alpha, ia64, and sparc64 architectures.
.Sh AUTHORS
.An Steve Passe Aq fsmp@FreeBSD.org