linux-kernel - Re: Reducing debuginfo size by removing unneeded includes

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Message-ID: <alpine.LFD.1.00.0802171456450.7583@apollo.tec.linutronix.de>
Date:	Sun, 17 Feb 2008 15:00:14 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: Reducing debuginfo size by removing unneeded includes

On Thu, 7 Feb 2008, Arnaldo Carvalho de Melo wrote:
> Hi Ingo,
> 
> 	I'm starting with you because the first file I used to
> experiment with this idea was arch/x86/ia32/sys_ia32.c.
> 
> 	I found it strange that the struct sk_buff definition was found
> inside the DWARF debugging sections in the generated object, so I verified
> and found that there is no need for the files that bring struct sk_buff
> definition into this file and verified also that sk_buff is not brought
> in indirectly too, thru other headers.
> 
> 	I went on and removed many other unneeded includes and the end
> result is:
> 
> [acme@...pio net-2.6]$ l /tmp/sys_ia32.o.before /tmp/sys_ia32.o.after
> -rw-rw-r-- 1 acme acme 185240 2008-02-06 19:19 /tmp/sys_ia32.o.after
> -rw-rw-r-- 1 acme acme 248328 2008-02-06 19:00 /tmp/sys_ia32.o.before
> 
> 	Almost 64KB only on this object file!
> 
> 	There were no other side effects from this change:
> 
> [acme@...pio net-2.6]$ objcopy -j "text" /tmp/sys_ia32.o.before /tmp/text.before
> [acme@...pio net-2.6]$ objcopy -j "text" /tmp/sys_ia32.o.after /tmp/text.after
> [acme@...pio net-2.6]$ md5sum /tmp/text.before /tmp/text.after
> b7ac9b17942add68494e698e4f965d36  /tmp/text.before
> b7ac9b17942add68494e698e4f965d36  /tmp/text.after
> 
> 	One of the complaints about using tools such as systemtap is
> that one has to install the huge kernel-debuginfo package:
> 
> [acme@...pio net-2.6]$ rpm -q --qf "%{size}\n" kernel-rt-debuginfo
> 471737710
> 543867594
> [acme@...pio net-2.6]$
> 
> 	So I'll try to improve automation to find more of these cases.

That'd be grat.
 
> 	Here goes the first patch, regards.

Applied. Thanks,

	 tglx
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