From 26f67c9caeda8cb513c46dac184d6941a3d4e6ef Mon Sep 17 00:00:00 2001
From: Joseph Koshy <jkoshy@FreeBSD.org>
Date: Sat, 18 Dec 2004 01:13:37 +0000
Subject: [PATCH] Document "machdep.hlt_cpus".

Reviewed by:	ru
---
 share/man/man4/smp.4 | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/share/man/man4/smp.4 b/share/man/man4/smp.4
index 28dacfcd16a3..198ac7ee3662 100644
--- a/share/man/man4/smp.4
+++ b/share/man/man4/smp.4
@@ -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 ,