linux-kernel - Re: [RFC][PATCH 5/3] tracing: Add smi counting to HWLAT

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Message-ID: <20160809143528.7bd9e4a0@gandalf.local.home>
Date:	Tue, 9 Aug 2016 14:35:28 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Clark Williams <williams@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jon Masters <jcm@...hat.com>, Daniel Wagner <wagi@...om.org>,
	Carsten Emde <C.Emde@...dl.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH 5/3] tracing: Add smi counting to HWLAT

On Tue, 9 Aug 2016 15:28:57 -0300
Daniel Bristot de Oliveira <bristot@...hat.com> wrote:

> On 08/09/2016 03:05 PM, Steven Rostedt wrote:
> > If an arch supports counting of SMIs (like newer intel chips do), then it
> > can implement arch_smi_count() to return the number of SMIs that were
> > triggered. The hwlat detector will call this function to get the current
> > number of SMIs, and then after a period, it will read that function again,
> > and if there's a difference, it will record that into the sample.
> > 
> > For example:
> > 
> >  [99] inner:13 outer:16 ts:1470352534.886878855
> >  [100] inner:14 outer:18747 ts:1470352538.917966818 smi-count:2
> >  [101] inner:0 outer:19162 ts:1470352539.920988709 smi-count:6
> >  [102] inner:19376 outer:19276 ts:1470352540.923010578 smi-count:6
> >  [103] inner:19650 outer:20665 ts:1470352541.926032469 smi-count:6
> >  [104] inner:20526 outer:20680 ts:1470352542.973055312 smi-count:6
> >  [105] inner:17 outer:17 ts:1470352543.990077507
> > 
> > Signed-off-by: Steven Rostedt <rostedt@...dmis.org>  
> 
> It worked fine in a system that I can manually cause SMIs (by turning
> keyboard's backlight on and off).
> 
> Tested-by: Daniel Bristot de Oliveira <bristot@...hat.com>

Thanks! I should also add:

Suggested-by: Peter Zijlstra <peterz@...radead.org>

As Peter was the one that recommended adding the arch_smi_count()
function.

But I can't push this yet as this would require acks from the x86
maintainers.

But if there's no complaints about the rest of the patches, I could
work to get that ready.

-- Steve