linux-kernel - Re: [PATCH 5/5] x86, nmi: Add better NMI stats to /proc/interrupts and show handlers

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Message-ID: <20140507163047.GB15779@gmail.com>
Date:	Wed, 7 May 2014 18:30:47 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
	ak@...ux.intel.com, gong.chen@...ux.intel.com,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 5/5] x86, nmi: Add better NMI stats to /proc/interrupts
 and show handlers


* Don Zickus <dzickus@...hat.com> wrote:

> On Wed, May 07, 2014 at 05:42:31PM +0200, Ingo Molnar wrote:
> > 
> > * Don Zickus <dzickus@...hat.com> wrote:
> > 
> > > The main reason for this patch is because I have a hard time knowing
> > > what NMI handlers are registered on the system when debugging NMI issues.
> > > 
> > > This info is provided in /proc/interrupts for interrupt handlers, so I
> > > added support for NMI stuff too.  As a bonus it provides stat breakdowns
> > > much like the interrupts.
> > > 
> > > The only ugly issue is how to label NMI subtypes using only 3 letters
> > > and still make it obvious it is part of the NMI.  Adding a /proc/nmi
> > > seemed overkill, so I choose to indent things by one space.  Sample
> > > output is below:
> > > 
> > > [root@...p71-248 ~]# cat /proc/interrupts
> > >            CPU0       CPU1       CPU2       CPU3
> > >   0:         29          0          0          0  IR-IO-APIC-edge      timer
> > > <snip>
> > > NMI:         20        774      10986       4227   Non-maskable interrupts
> > >  LOC:         21        775      10987       4228  Local     PMI, arch_bt
> > >  EXT:          0          0          0          0  External  plat
> > >  UNK:          0          0          0          0  Unknown
> > >  SWA:          0          0          0          0  Swallowed
> > > LOC:      30374      24749      20795      15095   Local timer interrupts
> > > SPU:          0          0          0          0   Spurious interrupts
> > > PMI:         20        774      10986       4227   Performance monitoring interrupts
> > > <snip>
> > 
> > Looks pretty useful!
> > 
> > The lost vertical alignment of the counts is a problem though IMHO.
> 
> Agreed!  It wasn't obvious to me at the time on how to keep that 
> alignment while only changing the first column.  I can look at it 
> again, if you are ok with the small shift in the first column.  
> Otherwise alternate ideas are welcomed. :-)

So I'd just pick a unique 3-letter shortcut for the first column and 
not do any shifting. Do the 'these are NMI sub-cases' distinction in 
the descripion field. Example mockup:

 NMI:         20        774      10986       4227   Non-maskable interrupts
 NLC:         21        775      10987       4228   NMI: Local PMI, arch_bt
 NXT:          0          0          0          0   NMI: External plat
 NUN:          0          0          0          0   NMI: Unknown
 NSW:          0          0          0          0   NMI: Swallowed
 LOC:      30374      24749      20795      15095   Local timer interrupts

or so.

Thanks,

	Ingo
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