linux-kernel - Re: [PATCH] Discardable strings for init and exit sections

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Message-ID: <20071012174507.GA21193@uranus.ravnborg.org>
Date:	Fri, 12 Oct 2007 19:45:07 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	Franck Bui-Huu <vagabon.xyz@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>, linux-arch@...r.kernel.org,
	linux-mips@...ux-mips.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Discardable strings for init and exit sections

On Fri, Oct 12, 2007 at 05:50:01PM +0100, Maciej W. Rozycki wrote:
>  We currently have infrastructure for discardable text and data, but no 
> such thing for strings.  This is especially notable for inline strings 
> such as ones used by printk() which are left behind resident in the memory 
> throughout the life of the system even though code referring to them has 
> been removed.

What is the actual benefit here expressed in real numbers?
For the __init/__exit notation that is yet only partially correct
we often see corner cases where one ask if it is really worth it.
Adding the discard functionality for strings seems like a logical extension
but there is a benefit/pain ratio to consider.

So real numbers please.

A few general notes to the patch.
1) We want to consolidate this in include/asm-generic/vmlinux*
somehow and this should be doen as a separate step.
2) If we introduce discardable strings then we shall in parallel
add build time checks so we catch strings marked as discardable
which is used outside a discardable compatible function.

	Sam
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