Re: [PATCH] NMI watchdog documentation

From: Mikael Pettersson (mikpe@csd.uu.se)
Date: Tue Jul 29 2003 - 05:37:33 EST


On Mon, 28 Jul 2003 19:53:42 +0200, Andi Kleen wrote:
>On Wed, 23 Jul 2003 20:43:25 +0300
>Ville Herva <vherva@niksula.hut.fi> wrote:
>
>> Documentation/nmi-watchdoc.txt doesn't actually tell what options need to be
>> enabled in kernel config in order to use NMI watchdog. I for one found it
>> confusing.
>>
>> I vaguely recall someone posted a similar patch some time ago, but it still
>> doesn't seem to be present in 2.4 or 2.6-test.
>>
>> Andi: what about x86-64 - does it have something similar that should be
>> mentioned?
>
>x86-64 is the same, except APIC is always compiled in and the nmi watchdog is
>always enabled with perfctr mode. mode=2 seems to also not work correctly currently.
>
>However one caveat (even for i386): when you use perfctr mode 1 you lose the first
>performance register which you may need for other things.

Andi, you have the numbers mixed up. mode 1 is I/O-APIC, mode 2 is local APIC,
and x86-64 defaults nmi_watchdog to I/O-APIC mode.
Now, is it the I/O-APIC or local APIC watchdog that doesn't work in x86-64?

/Mikael
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