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update smp related documentation after recent changes

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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)
This commit is contained in:
Andriy Gapon 2011-07-30 20:42:14 +00:00
parent 35edc49853
commit 235cc4c620
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=224528
3 changed files with 13 additions and 27 deletions
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6
release/doc/en_US.ISO8859-1/hardware/article.sgml
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@ -196,10 +196,8 @@
Because this naive scheduling can result in suboptimal
performance, under certain circumstances it may be useful to
disable the logical processors with the the
<varname>machdep.hlt_logical_cpus</varname> sysctl variable.
It is also possible to halt any CPU in the idle loop with the
<varname>machdep.hlt_cpus</varname> sysctl variable. The
&man.smp.4; manual page has more details.</para>
<varname>machdep.hyperthreading_allowed</varname> tunable.
The &man.smp.4; manual page has more details.</para>
<para>&os; will take advantage of Physical Address Extensions
(PAE) support on CPUs that support this feature. A kernel

14
share/man/man4/smp.4
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@ -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 ,

20
tools/tools/sysdoc/tunables.mdoc
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@ -1233,24 +1233,12 @@ machdep.disable_mtrrs
machdep.guessed_bootdev
---
machdep.hlt_cpus
machdep.hyperthreading_allowed
bool
This option will permit the halting
of CPUs.
For instance, to halt CPU 0,
machdep.htl_cpus=1 can be used.
It is possible to halt two CPUs by providing
a comma separated list (i.e: cpu1,cpu2).
---
machdep.hlt_logical_cpus
bool
This keeps the logical CPUs halted in the idle loop.
By default the logical CPUs are halted at startup.
It is also possible to halt any cpu in the idle loop now
using machdep.hlt_cpus.
Setting this tunable to zero disables
the use of additional logical processors
provided by Intel HTT technology.
---
machdep.panic_on_nmi