linux-kernel - Re: [patch 02/12] Immediate Values

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Message-ID: <20090928195444.GF1656@one.firstfloor.org>
Date:	Mon, 28 Sep 2009 21:54:45 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Jason Baron <jbaron@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Adrian Bunk <bunk@...sta.de>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [patch 02/12] Immediate Values - Architecture Independent Code

> btw just to add to this:
> caches are unified code/data after L1 in general... it then does not
> matter much if you encode the "almost constant" in the codestream or
> slightly farther away, in both cases it takes up cache space.

It does take up cache space, but when it's embedded in the instruction
stream the CPU has it usually already prefetched (CPUs are very good
at prefetching instructions). That's often not the case
with arbitary data accesses like this.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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