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

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Message-ID: <20081104204655.GG29626@one.firstfloor.org>
Date:	Tue, 4 Nov 2008 21:46:55 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	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

On Tue, Nov 04, 2008 at 12:26:13PM -0800, H. Peter Anvin wrote:
> Andi Kleen wrote:
> > 
> > Or again just generate them on demand when the interrupt is set up.
> > If you really have 240 interrupts sources you can afford the 5k likely,
> > but for most there will be only a minimum number of stubs.
> > 
> > Although frankly I suspect there are far easier ways to save 5k of memory.
> > 
> 
> Generating them dynamically is probably pretty ugly too, though.

Why? The only slightly tricky thing is that they need to be in no NX space.
Then it's just a few bytes patched in a template.

> Shrinking the whole table down to 2K by just regularizing the structure
> is trivial, though, and should almost certainly be a win.  The more
> esoteric ideas are probably worse.

Just think how much memory you could safe elsewhere with the same
effort.

-Andi
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