update smp related documentation after recent changes

Remove references to machdep.hlt_logical_cpus and
machdep.hlt_cpus sysctls and tunables.
Document machdep.hyperthreading_allowed and
hint.lapic.X.disabled tunables.

Prompted by:	ru
Proofreading:	bf
Reviewed by:	jhb
Approved by:	re (kib)

1 files changed, 7 insertions, 7 deletions

diff --git a/share/man/man4/smp.4 b/share/man/man4/smp.4
index 84c01bfeaa2c..5d0d983be183 100644
--- a/share/man/man4/smp.4
+++ b/share/man/man4/smp.4
@@ -63,10 +63,10 @@ the read-only sysctl variable
 .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
+This can be done using the
+.Va hint.lapic.X.disabled
+tunable, where X is the APIC ID of a CPU.
+Setting this tunable to 1 will result in the corresponding CPU being
 disabled.
 .Pp
 The
@@ -122,12 +122,12 @@ tasks on CPUs that are closely grouped together.
 supports hyperthreading on Intel CPU's on the i386 and AMD64 platforms.
 Since using logical CPUs can cause performance penalties under certain loads,
 the logical CPUs can be disabled by setting the
-.Va machdep.hlt_logical_cpus
-sysctl to one. 
-Note that this operation is different from the mechanism used by the
+.Va machdep.hyperthreading_allowed
+tunable to zero. 
 .Xr cpuset 1 .
 .Sh SEE ALSO
 .Xr mptable 1 ,
+.Xr loader 8 ,
 .Xr sysctl 8 ,
 .Xr condvar 9 ,
 .Xr msleep 9 ,