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

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Message-ID: <469E6335.8010708@zytor.com>
Date:	Wed, 18 Jul 2007 12:00:05 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Adrian Bunk <bunk@...sta.de>
CC:	Andi Kleen <andi@...stfloor.org>,
	Jonathan Campbell <jon@...dgrounds.com>,
	linux-kernel@...r.kernel.org, torvalds@...nsmeta.com
Subject: Re: Patches for REALLY TINY 386 kernels

Adrian Bunk wrote:
> On Wed, Jul 18, 2007 at 08:55:50AM -0700, H. Peter Anvin wrote:
>> Andi Kleen wrote:
>>>> 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.
>>>
>> Well, how big the vmlinux file is matters if it doesn't fit in memory
>> with enough time to get to the phase where it is dumping the init
>> sections.  *If that is not the issue*, then axing stuff like CPUID is a
>> major lose in terms of code maintainability for zero gain.
> 
> If this is an issue, then changing i386 back to discarding __exit code 
> and data at linktime instead of runtime might make a bigger difference.

What would really make a big difference would be to unspool the
initramfs in such a way that it only requires O(1) instead off O(n)
extra memory, by freeing memory as it decompresses and decodes the cpio
ball.

	-hpa
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