linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ville Herva <vherva@niksula.hut.fi>
To: Mikael Pettersson <mikpe@csd.uu.se>
Cc: ak@suse.de, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] NMI watchdog documentation
Date: Wed, 30 Jul 2003 22:40:52 +0300	[thread overview]
Message-ID: <20030730194052.GS83336@niksula.cs.hut.fi> (raw)
In-Reply-To: <200307301920.h6UJKXwC020610@harpo.it.uu.se>

On Wed, Jul 30, 2003 at 09:20:33PM +0200, you [Mikael Pettersson] wrote:
> On Tue, 29 Jul 2003 20:53:19 +0300, Ville Herva wrote:
> >On Tue, Jul 29, 2003 at 06:06:30PM +0200, you [Andi Kleen] wrote:
> >> > 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?
> >> 
> >> Right, 1 and 2 need to be exchanged. Anyways local apic mode does not seem
> >> to work, the kernel always reportss "NMI stuck" at bootup.
> >> IO APIC mode for is default.
> ...
> >+For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
> >+always enabled with perfctr mode. Currently, mode=1 does not work on x86-64.
> 
> Didn't Andi just say it's the other way around? nmi_watchdog=1 (I/O-APIC)
> by default since nmi_watchdog=2 (local APIC) doesn't work.

Ok, you got me confused (thankfully I didn't submit anything for inclusion
yet. :)

Initially, Andi said:

http://marc.theaimsgroup.com/?l=linux-kernel&m=105941508314399&w=2
> 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.

To which I replied:
http://marc.theaimsgroup.com/?l=linux-kernel&m=105942026020567&w=2
> So, is something like the following ok by you
>
> +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
> +always enabled with perfctr mode. Currently, mode=2 does not work on x86-64.
> +
> +Using NMI watchdog (in mode=1) needs the first performance register, so you
> +can't use it for other purposes (such as high precision performance
> +profiling.)

But you pointed out it was the other way around:
http://marc.theaimsgroup.com/?l=linux-kernel&m=105947532631384&w=2
> 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?

And Andi agreed:
http://marc.theaimsgroup.com/?l=linux-kernel&m=105949540722325&w=2
> Right, 1 and 2 need to be exchanged. Anyways local apic mode does not seem
> to work, the kernel always reportss "NMI stuck" at bootup. IO APIC mode
> for is default.

So I proposed (blindly exchanging the numbers):
http://marc.theaimsgroup.com/?l=linux-kernel&m=105950174531125&w=2
> +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
> +always enabled with perfctr mode. Currently, mode=1 does not work on x86-64.
> +
> +Using NMI watchdog (in mode=2) needs the first performance register, so you
> +can't use it for other purposes (such as high precision performance
> +profiling.)

So... Should it be something like:

+For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
+always enabled with perctr mode. Currently, mode=2 (local APIC) does not
+work on x86-64. IO APIC mode (mode=1) is the default. Using NMI watchdog
+(mode=1) needs the first performance register, so you can't use it for
+other purposes (such as high precision performance profiling.)

(Is the last sentence only valid for x86-64?)


-- v --

v@iki.fi

  reply	other threads:[~2003-07-30 19:41 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-07-30 19:20 [PATCH] NMI watchdog documentation Mikael Pettersson
2003-07-30 19:40 ` Ville Herva [this message]
  -- strict thread matches above, loose matches on Subject: below --
2003-07-31 21:25 Mikael Pettersson
2003-07-30 22:53 Mikael Pettersson
2003-07-31  5:44 ` Ville Herva
2003-07-30 19:18 Mikael Pettersson
2003-07-29 10:37 Mikael Pettersson
2003-07-29 16:06 ` Andi Kleen
2003-07-29 17:53   ` Ville Herva
2003-07-23 17:43 Ville Herva
2003-07-28 17:53 ` Andi Kleen
2003-07-28 19:21   ` Ville Herva

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20030730194052.GS83336@niksula.cs.hut.fi \
    --to=vherva@niksula.hut.fi \
    --cc=ak@suse.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mikpe@csd.uu.se \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).