mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-19 10:53:58 +00:00
110 lines
3.5 KiB
Groff
110 lines
3.5 KiB
Groff
.\" Copyright (c) 1997
|
|
.\" Steve Passe <fsmp@FreeBSD.ORG>. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. The name of the developer may NOT be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 17, 2004
|
|
.Dt SMP 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm SMP
|
|
.Nd description of the FreeBSD Symmetric Multi-Processor kernel
|
|
.Sh SYNOPSIS
|
|
.Cd options SMP
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
kernel implements symmetric multi-processor support.
|
|
.Sh COMPATIBILITY
|
|
Support for multi-processor systems is present for all Tier-1
|
|
architectures on
|
|
.Fx .
|
|
Currently, this includes amd64, 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
|
|
The number of CPUs detected by the system is available in
|
|
the read-only sysctl variable
|
|
.Va hw.ncpu .
|
|
.Pp
|
|
.Fx
|
|
allows specific CPUs on a multi-processor system to be disabled.
|
|
The sysctl variable
|
|
.Va machdep.hlt_cpus
|
|
is an integer bitmask denoting CPUs to halt, counting from 0.
|
|
Setting a bit to 1 will result in the corresponding CPU being
|
|
disabled.
|
|
.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 sysctl 8 ,
|
|
.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 ia64, and sparc64 architectures.
|
|
.Sh AUTHORS
|
|
.An Steve Passe Aq fsmp@FreeBSD.org
|