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

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