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x86: nmi_watchdog - documentation fix 

nmi_watchdog is set to NMI_NONE by default (ie disabled) on _any_
mode so lets fix documentation too.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Cyrill Gorcunov 2008-06-27 19:43:40 +04:00 committed by Ingo Molnar
parent 914bebfad4
commit afda335dc3
1 changed files with 7 additions and 9 deletions
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Documentation/nmi_watchdog.txt
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@ -22,8 +22,7 @@ CONFIG_X86_UP_IOAPIC is for uniprocessor with an IO-APIC. [Note: certain
kernel debugging options, such as Kernel Stack Meter or Kernel Tracer, kernel debugging options, such as Kernel Stack Meter or Kernel Tracer,
may implicitly disable the NMI watchdog.] may implicitly disable the NMI watchdog.]
For x86-64, the needed APIC is always compiled in, and the NMI watchdog is For x86-64, the needed APIC is always compiled in.
always enabled with I/O-APIC mode (nmi_watchdog=1).
Using local APIC (nmi_watchdog=2) needs the first performance register, so Using local APIC (nmi_watchdog=2) needs the first performance register, so
you can't use it for other purposes (such as high precision performance you can't use it for other purposes (such as high precision performance
@ -67,12 +66,11 @@ time. The I/O APIC watchdog is driven externally and has no such shortcoming.
But its NMI frequency is much higher, resulting in a more significant hit But its NMI frequency is much higher, resulting in a more significant hit
to the overall system performance. to the overall system performance.
NOTE: starting with 2.4.2-ac18 the NMI-oopser is disabled by default, On x86 nmi_watchdog is disabled by default so you have to enable it with
you have to enable it with a boot time parameter. Prior to 2.4.2-ac18 a boot time parameter.
the NMI-oopser is enabled unconditionally on x86 SMP boxes.
On x86-64 the NMI oopser is on by default. On 64bit Intel CPUs NOTE: Prior to 2.4.2-ac18 the NMI-oopser is enabled unconditionally
it uses IO-APIC by default and on AMD it uses local APIC. on x86 SMP boxes.
[ feel free to send bug reports, suggestions and patches to [ feel free to send bug reports, suggestions and patches to
Ingo Molnar <mingo@redhat.com> or the Linux SMP mailing Ingo Molnar <mingo@redhat.com> or the Linux SMP mailing