1.\" Copyright (c) 1997 2.\" Steve Passe <fsmp@FreeBSD.ORG>. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. The name of the developer may NOT be used to endorse or promote products 10.\" derived from this software without specific prior written permission. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.\" $FreeBSD$ 25.\" 26.Dd December 5, 2002 27.Dt SMP 4 28.Os 29.Sh NAME 30.Nm SMP 31.Nd description of the FreeBSD Symmetric MultiProcessor kernel 32.Sh SYNOPSIS 33.Cd options SMP 34.Sh DESCRIPTION 35The 36.Nm 37kernel implements symmetric multiprocessor support. 38.Sh COMPATIBILITY 39Support for multi-processor systems is present for all Tier-1 40architectures on 41.Fx . 42Currently, this includes alpha, i386, ia64, and sparc64. 43Support is enabled using 44.Cd options SMP . 45It is permissible to use the SMP kernel configuration on non-SMP equipped 46motherboards. 47.Sh I386 NOTES 48For i386 systems, the 49.Nm 50kernel supports motherboards that follow the Intel MP specification, 51version 1.4. 52In addition to 53.Cd options SMP , 54i386 also requires 55.Cd device apic . 56The 57.Xr mptable 1 58command may be used to view the status of multi-processor support. 59.Pp 60.Fx 61supports hyperthreading on Intel CPU's on the i386 platform. 62Since using logical CPUs can cause performance penalties under certain loads, 63the logical CPUs can be disabled by setting the 64.Va machdep.hlt_logical_cpus 65sysctl to one. 66.Sh SEE ALSO 67.Xr mptable 1 , 68.Xr condvar 9 , 69.Xr msleep 9 , 70.Xr mtx_pool 9 , 71.Xr mutex 9 , 72.Xr sema 9 , 73.Xr sx 9 74.Sh HISTORY 75The 76.Nm 77kernel's early history is not (properly) recorded. 78It was developed 79in a separate CVS branch until April 26, 1997, at which point it was 80merged into 3.0-current. 81By this date 3.0-current had already been 82merged with Lite2 kernel code. 83.Pp 84.Fx 5.0 85introduced support for a host of new synchronization primitives, and 86a move towards fine-grained kernel locking rather than reliance on 87a Giant kernel lock. 88The SMPng Project relied heavily on the support of BSDi, who provided 89reference source code from the fine-grained SMP implementation found 90in 91.Bsx . 92.Pp 93.Fx 5.0 94also introduced support for SMP on the alpha, ia64, and sparc64 architectures. 95.Sh AUTHORS 96.An Steve Passe Aq fsmp@FreeBSD.org 97