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

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Message-ID: <20081104171346.GF21470@localhost>
Date:	Tue, 4 Nov 2008 20:13:46 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alexander van Heukelum <heukelum@...tmail.fm>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, lguest@...abs.org,
	jeremy@...source.com, Steven Rostedt <srostedt@...hat.com>,
	Mike Travis <travis@....com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

[Ingo Molnar - Tue, Nov 04, 2008 at 05:58:11PM +0100]
| 
| * Cyrill Gorcunov <gorcunov@...il.com> wrote:
| 
| > [Alexander van Heukelum - Tue, Nov 04, 2008 at 05:23:09PM +0100]
| > ...
| > | 
| > | I did some timings using the little program below (32-bit only), doing
| > | 1024 times the same sequence. TEST1 is just pushing a constant onto
| > | the stack; TEST2 is pushing the cs register; TEST3 is the sequence
| > | from the patch to extract the vector number from the cs register.
| > | 
| > | Opteron    (cycles): 1024 / 1157 / 3527
| > | Xeon E5345 (cycles): 1092 / 1085 / 6622
| > | Athlon XP  (cycles): 1028 / 1166 / 5192
| > 
| > Xeon is defenitely out of luck :-)
| 
| it's still OK - i.e. no outrageous showstopper overhead anywhere in 
| that instruction sequence. The total round-trip overhead is what will 
| matter most.
| 
| 	Ingo
| 

Don't get me wrong please, I really like what Alexander have done!
But frankly six time slower is a bit scarying me.

		- Cyrill -
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