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 . 45On most platforms it is permissible to use the SMP 46kernel configuration on non-SMP equipped motherboards. 47The only exception to this rule is the i386 platform. 48.Pp 49For i386 systems, the 50.Nm 51kernel supports motherboards that follow the Intel MP specification, 52version 1.4. 53In addition to 54.Cd options SMP , 55i386 also requires 56.Cd options APIC_IO . 57The 58.Xr mptable 1 59command may be used to view the status of multi-processor support. 60.Pp 61.Fx 62supports hyperthreading on Intel CPU's on the i386 platform. 63By default, logical CPUs are not used to execute user processes due to 64performance penalties under common loads. 65To allow the logical CPUs to execute user processes, 66turn off the 67.Va machdep.hlt_logical_cpus 68sysctl by setting its value to zero. 69.Sh SEE ALSO 70.Xr mptable 1 , 71.Xr condvar 9 , 72.Xr msleep 9 , 73.Xr mtx_pool 9 , 74.Xr mutex 9 , 75.Xr sema 9 , 76.Xr sx 9 77.Sh HISTORY 78The 79.Nm 80kernel's early history is not (properly) recorded. 81It was developed 82in a separate CVS branch until April 26, 1997, at which point it was 83merged into 3.0-current. 84By this date 3.0-current had already been 85merged with Lite2 kernel code. 86.Pp 87.Fx 5.0 88introduced support for a host of new synchronization primitives, and 89a move towards fine-grained kernel locking rather than reliance on 90a Giant kernel lock. 91The SMPng Project relied heavily on the support of BSDi, who provided 92reference source code from the fine-grained SMP implementation found 93in 94.Bsx . 95.Pp 96.Fx 5.0 97also introduced support for SMP on the alpha, ia64, and sparc64 architectures. 98.Sh AUTHORS 99.An Steve Passe Aq fsmp@FreeBSD.org 100