Message-ID: <4910AA51.3070602@goop.org>
Date: Tue, 04 Nov 2008 12:02:25 -0800
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Ingo Molnar <mingo@elte.hu>
CC: Alexander van Heukelum <heukelum@fastmail.fm>,
       Alexander van Heukelum <heukelum@mailshack.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       lguest@ozlabs.org, jeremy@xensource.com,
       Steven Rostedt <srostedt@redhat.com>,
       Cyrill Gorcunov <gorcunov@gmail.com>, Mike Travis <travis@sgi.com>,
       Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes
References: <20081104122839.GA22864@mailshack.com> <20081104124242.GA6795@elte.hu> <1225805399.25337.1282903253@webmail.messagingengine.com> <20081104140030.GA16178@elte.hu>
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Ingo Molnar wrote:
> ( another advantage is that the 6 bytes GDT descriptor is more 
>   compressed and hence uses up less L1/L2 cache footprint than the 
>   larger (~7 byte) trampolines we have at the moment. )
>   

Also its D cache rather than I cache, which is generally more 
plentiful.  However, I think the cost of GDT cache misses on exception 
latency is something that we've largely overlooked, and this will make 
it a bigger factor (vs cache misses on the actual exception handler code 
itself, which should be reduced).

    J
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