Message-ID: <4910C014.9070805@zytor.com>
Date: Tue, 04 Nov 2008 13:35:16 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Alexander van Heukelum <heukelum@fastmail.fm>,
       Andi Kleen <andi@firstfloor.org>, Cyrill Gorcunov <gorcunov@gmail.com>,
       Alexander van Heukelum <heukelum@mailshack.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>, lguest@ozlabs.org,
       jeremy@xensource.com, Steven Rostedt <srostedt@redhat.com>,
       Mike Travis <travis@sgi.com>
Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes
References: <20081104122839.GA22864@mailshack.com> <20081104150729.GC21470@localhost> <20081104170501.GE29626@one.firstfloor.org> <1225822006.21441.1282961299@webmail.messagingengine.com> <20081104204400.GC10825@elte.hu> <20081104212933.GA11050@elte.hu>
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Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.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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