linux-kernel - Re: [PATCH v3 0/3] Add support for compiling with -ffunction-sections -fdata-sections

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Message-ID: <20090424001439.GA27897@linux-sh.org>
Date:	Fri, 24 Apr 2009 09:14:40 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Tim Abbott <tabbott@....EDU>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Anders Kaseorg <andersk@....edu>,
	Waseem Daher <wdaher@....edu>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Jeff Arnold <jbarnold@....edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jon Masters <jonathan@...masters.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Theodore Ts'o <tytso@....edu>,
	Nikanth Karthikesan <knikanth@...e.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Am?rico Wang <xiyou.wangcong@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Kyle McMartin <kyle@...artin.ca>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH v3 0/3] Add support for compiling with -ffunction-sections -fdata-sections

On Thu, Apr 23, 2009 at 04:48:52PM -0400, Tim Abbott wrote:
> On Mon, 20 Apr 2009, Linus Torvalds wrote:
> 
> > I'd be ok with merging it, but I haven't really gotten a strong feeling 
> > that anybody is going to enable it or use it.
> 
> Linus,
> 
> Would you be willing to merge the first 3 patches in this patch series at 
> this point?  I'm resending these patches to resolve some conflicts that 
> was recently introduced.
> 
> To summarize the discussion, there are three uses for this code that have 
> significant interest.
> 
> One is decreasing the kernel size.  Denys Vlasenko has numbers that using 
> the linker's --gc-sections option (for which these patches are a 
> prerequisite) saves 10% of the kernel size when CONFIG_MODULES=n, and 1% 
> when CONFIG_MODULES=y.  Paul Mundt thinks many embedded users would use 
> this if it were available.
> 
> A related use is cleaning up a lot of ifdefs that exist only to decrease 
> the kernel size.  Several developers commented favorably on the direction 
> of using section garbage collection for dead code removal.
> 
> Finally, Ksplice depends on the option added by this patch series.
> 
> The first 3 patches in this patch series fix problems associated with 
> using -ffunction-sections.  As there are some architectures currently 
> using -ffunction-sections, these should ideally be merged now, especially 
> the first patch which involves scattered changes.
> 
Given that this fixes issues with the existing in-tree users, it would
help to make them aware of this also.. added to the CC.
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