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

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Date:	Mon, 10 Nov 2008 21:00:53 -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

Okay, after spending most of the day trying to get something that isn't
completely like white noise (interesting problem, otherwise I'd have
given up long ago) I did, eventually, come up with something that looks
like it's significant.  I did a set of multiple runs, and am looking for
the "waterfall points" in the cumulative statistics.

http://www.zytor.com/~hpa/baseline-hpa-3000-3600.pdf

This particular set of data points was gathered on a 64-bit kernel, so I
didn't try the segment technique.

It looks to me that the collection of red lines is enough to the left of
the black ones that one can assume there is a significant effect,
probably by about a cache miss worth of time.

	-hpa

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