linux-kernel - Re: [PATCH 0/3] build system: section garbage collection for vmlinux

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Message-Id: <200709071830.17027.vda.linux@googlemail.com>
Date:	Fri, 7 Sep 2007 18:30:16 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	sam@...nborg.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] build system: section garbage collection for vmlinux

On Friday 07 September 2007 17:31, Daniel Walker wrote:
> On Thu, 2007-09-06 at 18:07 +0100, Denys Vlasenko wrote:
> > A bit extended version:
> > 
> > In the process in making it work I saw ~10% vmlinux size reductions
> > (which basically matches what Marcelo says) when I wasn't retaining
> > sections needed for EXPORT_SYMBOLs, but module loading didn't work.
> > 
> > Thus I fixed that by adding KEEP() directives so that EXPORT_SYMBOLs
> > are never discarded. This was just one of many fixes until kernel
> > started to actually boot and work.
> > 
> > I did that before I posted patches to lkml.
> > IOW: posted patches are not broken versus module loading.
> 
> Ok, this is more like the explanation I was looking for..
> 
> During this thread you seemed to indicate the patches you release
> reduced the kernel ~10% , but now your saying that was pre-release ,
> right?

CONFIG_MODULE=n will save ~10%
CONFIG_MODULE=y - ~1%

Exact figure depends on .config (whether you happen to include
especially "fat" code or not).

I want to explain a bit where I am coming from. I am working on busybox,
and last release made busybox smaller by "whopping" 2%. This is the result
of a hundred or so of small code and data shrinks.

It basically means that I am close to the point of diminishing returns
trying to make busybox smaller, and memory wastage on the running
embedded system is now elsewhere - including kernel.
--
vda
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