linux-kernel - Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

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Date:	Mon, 10 Nov 2008 15:34:59 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
CC:	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>, lguest@...abs.org,
	jeremy@...source.com, Steven Rostedt <srostedt@...hat.com>,
	Mike Travis <travis@....com>
Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

Alexander van Heukelum wrote:
> 
> I did the rdtsctest again for the irqstubs patch you sent. The data
> is at http://heukelum.fastmail.fm/irqstubs/ and the latency histogram
> is http://heukelum.fastmail.fm/irqstubs/latency_hpa.png
> 

Okay, I've stared at a bunch of different transformations of this data
and I'm starting to think that it's getting lost in the noise.  The
difference between your "idleticks" and "idleticks2" data sets, for
example, is as big as the differences between any two data sets that I
can see.

Just for reference, see this graph where I have filtered out events
outside the [30..1000] cycle range and renormalized.

	http://www.zytor.com/~hpa/hist.pdf

I don't know how to even figure out what a realistic error range looks
like, other than repeating each run something like 100+ times and do an
"eye chart" kind of diagram.

	-hpa
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