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Document "machdep.hlt_cpus".

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Reviewed by:	ru
This commit is contained in:
Joseph Koshy 2004-12-18 01:13:37 +00:00
parent 41ecd18235
commit 26f67c9cae
1 changed files with 16 additions and 3 deletions
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19
share/man/man4/smp.4
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@ -23,18 +23,18 @@
.\"
.\" $FreeBSD$
.\"
.Dd December 5, 2002
.Dd December 17, 2004
.Dt SMP 4
.Os
.Sh NAME
.Nm SMP
.Nd description of the FreeBSD Symmetric MultiProcessor kernel
.Nd description of the FreeBSD Symmetric Multi-Processor kernel
.Sh SYNOPSIS
.Cd options SMP
.Sh DESCRIPTION
The
.Nm
kernel implements symmetric multiprocessor support.
kernel implements symmetric multi-processor support.
.Sh COMPATIBILITY
Support for multi-processor systems is present for all Tier-1
architectures on
@ -57,6 +57,18 @@ 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,
@ -65,6 +77,7 @@ the logical CPUs can be disabled by setting the
sysctl to one.
.Sh SEE ALSO
.Xr mptable 1 ,
.Xr sysctl 8 ,
.Xr condvar 9 ,
.Xr msleep 9 ,
.Xr mtx_pool 9 ,