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

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Message-ID: <p737ioyxwyq.fsf@bingen.suse.de>
Date:	18 Jul 2007 04:33:01 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jonathan Campbell <jon@...dgrounds.com>
Cc:	linux-kernel@...r.kernel.org, torvalds@...nsmeta.com
Subject: Re: Patches for REALLY TINY 386 kernels

Jonathan Campbell <jon@...dgrounds.com> writes:

> 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.

I'm afraid a lot of this, like the CPUID changes, are fairly pointless
because they are  __cpuinit code anyways. This means (unless you compiled
a kernel with CPU hotplug support enabled) it will be all freed after
boot.

> Already with these patches I can compile a zImage kernel that is 450kb
> large (890kb decompressed)

The important part is not how big the vmlinux is, but how much
memory is actually used after boot. 

I expect concentrating some of the dynamic data structures would
be more fruitful in fact.

-Andi
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