Date: Tue, 7 Mar 2017 08:42:10 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Mike Travis <mike.travis@hpe.com>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Don Zickus <dzickus@redhat.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Dimitri Sivanich <dimitri.sivanich@hpe.com>,
        Frank Ramsay <frank.ramsay@hpe.com>,
        Russ Anderson <russ.anderson@hpe.com>, Tony Ernst <tony.ernst@hpe.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86/platform: Add a low priority low frequency NMI
 call chain
Message-ID: <20170307074210.GA24782@gmail.com>
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* Mike Travis <mike.travis@hpe.com> wrote:

> Add a new NMI call chain that is called last after all other NMI handlers
> have been checked and did not "handle" the NMI.  This mimics the current
> NMI_UNKNOWN call chain except it eliminates the WARNING message about
> multiple NMI handlers registering on this call chain.
> 
> This call chain dramatically lowers the NMI call frequency when high
> frequency NMI tools are in use, notably the perf tools.  It is required
> for NMI handlers that cannot sustain a high NMI call rate without
> ramifications to the system operability.

So how about we just turn off that warning instead? I don't remember the last time 
it actually _helped_ us find any kernel or hardware bug - and it has caused tons 
of problems...

It's not like we warn about excess regular IRQs either - we either handle them or 
at most increase a counter somewhere. We could do the same for NMIs: introduce a 
counter somewhere that counts the number of seemingly unhandled NMIs.

But in any case, we should not spam the kernel log, neither with high, nor with 
low frequency.

Thanks,

	Ingo