Date: Sat, 24 May 2003 15:08:19 -0400 (EDT)
From: Zwane Mwaikambo <zwane@linuxpower.ca>
To: Carl-Daniel Hailfinger <c-d.hailfinger.kernel.2003@gmx.net>
cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       "" <linux-smp@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>
Subject: Re: [RFC] Fix NMI watchdog documentation
In-Reply-To: <3ECFC2D6.2020007@gmx.net>
Message-ID: <Pine.LNX.4.50.0305241505470.2267-100000@montezuma.mastecende.com>
References: <3ECFC2D6.2020007@gmx.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1405
Lines: 31

On Sat, 24 May 2003, Carl-Daniel Hailfinger wrote:

> Documentation/nmi_watchdog.txt does not say which CONFIG_XYZ option has
> to be enabled to use the NMI watchdog, but it mentions that IO-APIC is
> somewhat related.
> 
> Documentation/Configure.help is equally unclear. The NMI watchdog is
> mentioned as related to CONFIG_SMP, and the help text for
> CONFIG_X86_UP_APIC says: "The local APIC supports [..] the NMI watchdog"
> That does not necessarily mean that NMI is compiled in once local APIC
> support is selected.
> 
> Can someone please shed some light on this issue? I'm willing to create
> a patch to fix the docs once I know if the NMI watchdog is compiled in
> alsways or on what it depends.

For nmi_watchdog=1 the NMI watchdog uses the programmable interval timer
to trigger interrupt events via the IOAPIC. with nmi_watchdog=2 we use the 
performance counters on the processor to trigger these events. IOAPICs 
are generally found on SMP motherboards (but there are UP boards with 
them, it's chipset dependent). Generally i686+ (save some Athlons and a 
few other processors) will work with nmi_watchdog=2.

	Zwane
-- 
function.linuxpower.ca
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/