Message-ID: <46F15ED4.40002@zytor.com>
Date: Wed, 19 Sep 2007 10:39:32 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       Andi Kleen <ak@muc.de>, Chuck Ebbert <cebbert@redhat.com>,
       Christoph Hellwig <hch@infradead.org>
Subject: Re: [patch 4/7] Immediate Values - i386 Optimization
References: <20070918210747.828804366@polymtl.ca> <20070918210853.588573678@polymtl.ca> <46F04856.3010808@goop.org> <46F04D53.6040903@zytor.com> <46F050E8.5020206@goop.org> <20070919130122.GA21750@Krystal> <46F14A58.60904@zytor.com> <46F15CB8.6010408@goop.org>
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Jeremy Fitzhardinge wrote:
> 
> Cross-cache-line, sure.  But what about just not sizeof aligned?  If its
> enough to avoid cross-cache-line, then that's simpler.
> 

Not really.  It pretty much comes down to the same problem.

> Which is something I was going to comment on: Mathieu, you try to align
> the constant itself, but you don't prevent the instruction overall from
> crossing a cache line.  Given how delicate all this stuff is, it seems
> like a good idea to do that.

Given how delicate all his stuff is, it would be interesting to know the
magnitude of the expected payoff, which I personally don't remember seeing.

	-hpa

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