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

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Message-ID: <4910C014.9070805@zytor.com>
Date:	Tue, 04 Nov 2008 13:35:16 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Alexander van Heukelum <heukelum@...tmail.fm>,
	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

Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
>> And as hpa's comments point it out, compressing the rather stupid 
>> irq stubs might be a third option that looks promising as well.
> 
> ... and we should try and see how far we can compress those stubs, 
> before we do any segment register based tricks.
> 

Using the techniques previously mentioned, for 224 vectors:

1792 bytes ( 8 bytes/stub) - trivial.
1568 bytes ( 7 bytes/stub) - same without alignment.
 952 bytes (~4 bytes/stub) - extra jump needed.

For comparison, the IDT itself is 2048 bytes on x86-32 and 4096 bytes on
x86-64.

	-hpa
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