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Re: Latest sources from CVS.

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Latest sources from CVS.
From: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
Date: Fri, 6 Dec 2002 18:15:19 +0100
Cc: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, Carsten Langgaard <carstenl@mips.com>, "Kevin D. Kissell" <kevink@mips.com>, linux-mips@linux-mips.org
In-reply-to: <20021206180241.A7492@linux-mips.org>
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References: <20021206135110.GD23743@rembrandt.csv.ica.uni-stuttgart.de> <Pine.GSO.3.96.1021206165118.26674N-100000@delta.ds2.pg.gda.pl> <20021206164558.GH23743@rembrandt.csv.ica.uni-stuttgart.de> <20021206180241.A7492@linux-mips.org>
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Ralf Baechle wrote:
> On Fri, Dec 06, 2002 at 05:45:58PM +0100, Thiemo Seufer wrote:
> 
> > > If we want to preserve the setup cleanly, we
> > > probably need yet another ABI model in gcc (especially in the face of the
> > > coming changes to get rid of assembly macros), with sign-extended 32-bit
> > > pointers for accessing program segments and 64-bit ones for the remaining
> > > addresses.
> > 
> > Do you think this is worth the hassle? N64 offers better flexibility in
> > the large memory case at some performance cost, and it's conceptionally
> > cleaner.
> 
> Absolutely:
> 
> [ralf@dea linux-sgi-2.4]$ mips64-linux-size vmlinux
>    text    data     bss     dec     hex filename
> 1978296  317344  156224 2451864  256998 vmlinux
> [ralf@dea linux-sgi-2.4]$ mips64-linux-size vmlinux
>    text    data     bss     dec     hex filename
> 1761168  317344  156224 2234736  221970 vmlinux
> 
> The first kernel was built as 64-bit ELF using 64-bit pointer and everything
> 64-bit.  The second kernel was built using the -Wa,-32 trick.  That's over
> 12% of bloat for full 64-bitiness which brings zero gain.

I found that in the first case the text segment of my linux kernels
has trailing garbage in it, which can explain most of the difference.

I haven't looked into it yet, it seems to be harmless besides of
increasing file and memory size.

Could you have a look at the disassembly, I guess your kernels suffer
the same effect.


Thiemo

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