linux-kernel - Re: [patch 12/17] Immediate Values

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Message-Id: <200804101323.56697.rusty@rustcorp.com.au>
Date:	Thu, 10 Apr 2008 13:23:55 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Adrian Bunk <bunk@...sta.de>,
	Christoph Hellwig <hch@...radead.org>, akpm@...l.org
Subject: Re: [patch 12/17] Immediate Values - Kconfig menu in EMBEDDED

On Thursday 10 April 2008 01:08:41 Mathieu Desnoyers wrote:
> +config IMMEDIATE
> +	default y if !DISABLE_IMMEDIATE

Wouldn't it be simlpler to roll DISABLE_IMMEDIATE into this?

ie.
	default y
	depends on HAVE_IMMEDIATE
	bool "Immediate value optimization" if EMBEDDED
	help
	  Immediate values are used as read-mostly variables that are rarely
	  updated. They use code patching to modify the values inscribed in the
	  instruction stream. It provides a way to save precious cache lines
	  that would otherwise have to be used by these variables.

	  It consumes slightly more memory and requires to modify the instruction
	  stream each time a variable is updated. Should really be disabled for
	  embedded systems with read-only text.

Cheers,
Rusty.
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