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

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Message-ID: <4911E3E7.6090109@zytor.com>
Date:	Wed, 05 Nov 2008 10:20:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Andi Kleen <andi@...stfloor.org>,
	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

Cyrill Gorcunov wrote:
> 
> I see. Thanks! Btw Peter, I remember I read long time ago about
> segment caches (well... in time of DOS programming actually). But
> there was only 'common' words like this cache exist. But maybe
> it's possible to know what exactly size of such a cache is?
> You mentoined number 32. (heh... I hadn't remember it until
> you mentoined about such a cache :-)
> 

As with any other caching structure, you can discover its size,
associativity, and replacement policy by artificially trying to provoke
patterns that produce pathological timings.

At Transmeta, at one time we used a 32-entry direct-mapped cache, which
ended up with a ~96% hit rate on common Win95 benchmarks.

I should, however, make it clear that there are other alternatives for
speeding up segment descriptor loading, and not all of them rely on a cache.

	-hpa
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