FreeBSD Manual Pages
SMP(4) FreeBSD Kernel Interfaces Manual SMP(4) NAME SMP -- description of the FreeBSD Symmetric MultiProcessor kernel SYNOPSIS options SMP DESCRIPTION The SMP kernel implements symmetric multiprocessor support. COMPATIBILITY Support for multi-processor systems is present for all Tier-1 architec- tures on FreeBSD. Currently, this includes alpha, i386, ia64, and sparc64. Support is enabled using options SMP. On most platforms it is permissible to use the SMP kernel configuration on non-SMP equipped moth- erboards. The only exception to this rule is the i386 platform. For i386 systems, the SMP kernel supports motherboards that follow the Intel MP specification, version 1.4. In addition to options SMP, i386 also requires options APIC_IO. The mptable(1) command may be used to view the status of multi-processor support. FreeBSD supports hyperthreading on Intel CPU's on the i386 platform. By default, logical CPUs are not used to execute user processes due to per- formance penalties under common loads. To allow the logical CPUs to exe- cute user processes, turn off the machdep.hlt_logical_cpus sysctl by set- ting its value to zero. SEE ALSO mptable(1), condvar(9), msleep(9), mtx_pool(9), mutex(9), sema(9), sx(9) HISTORY The SMP kernel's early history is not (properly) recorded. It was devel- oped 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. FreeBSD 5.0 introduced support for a host of new synchronization primi- tives, 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 BSD/OS. FreeBSD 5.0 also introduced support for SMP on the alpha, ia64, and sparc64 architectures. AUTHORS Steve Passe <fsmp@FreeBSD.org> FreeBSD 11.1 December 5, 2002 FreeBSD 11.1
NAME | SYNOPSIS | DESCRIPTION | COMPATIBILITY | SEE ALSO | HISTORY | AUTHORS
Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=smp&sektion=4&manpath=FreeBSD+5.2-RELEASE>