linux-kernel - Re: Patches for REALLY TINY 386 kernels

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Message-ID: <20070715230524.GL3565@stusta.de>
Date:	Mon, 16 Jul 2007 01:05:24 +0200
From:	Adrian Bunk <bunk@...sta.de>
To:	Jonathan Campbell <jon@...dgrounds.com>
Cc:	linux-kernel@...r.kernel.org, torvalds@...nsmeta.com
Subject: Re: Patches for REALLY TINY 386 kernels

On Sun, Jul 15, 2007 at 02:00:29PM -0700, Jonathan Campbell wrote:
> I wrote a set of patches out of concern that even if you compile a 386 
> kernel a lot of code irrelevent to legacy machines still remains. Things 
> like the Pentium TSC register, DMI information, ESCD parsing, and the use 
> of CPUID do not apply to these machines, but looking at System.map you can 
> see they're still there.
>
> Already with these patches I can compile a zImage kernel that is 450kb 
> large (890kb decompressed) with a small initramfs payload, floppy and 
> kernel module support, FPU emulation, that can successfully boot on an 
> ancient 386 laptop with only 1MB of extended memory. Eventually what I'd 
> like to have is the ability to compile a pure 386 kernel with all non-386 
> functions removed (and perhaps the same for 486 machines).
>...

Besides some issues with the patch itself you didn't provide the one 
important number:
By how much does your patch decrease the size of the kernel?

Also note that when aiming for a tiny kernel enabling module support is 
a huge mistake since it increases the amount of RAM used when running 
the kernel by at about 10%.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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