linux-kernel - Re: [PATCH] init: bzip2 or lzma -compressed kernels and initrds

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Date:	Mon, 8 Sep 2008 15:14:40 +0200
From:	Jörn Engel <joern@...fs.org>
To:	Rob Landley <rob@...dley.net>
Cc:	Alain Knaff <alain@...ff.lu>,
	Leon Woestenberg <leon.woestenberg@...il.com>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init: bzip2 or lzma -compressed kernels and initrds

On Sun, 7 September 2008 01:17:55 -0500, Rob Landley wrote:
> 
> I vaguely recall that lzma requires more memory to decompress than bzip2 does, 
> although I don't remember the details.  I know that bzip2 takes around 4 megs 
> (although you need space for the decompressed kernel on _top_ of that, so you 
> should be able to do it in about 8 megs total).  gunzip uses a 64k sliding 
> window plus dictionary and the whole mess should fit in about 1/4 of a meg.

Less, actually.  Iirc gzip takes about 280k for compression and
somewhere below 100k for decompression with the kernel runtime zlib.
The various copies that unpack kernels at boottime may be worse - they
are certainly rather old copies of zlib and haven't seen much
maintenance since.

Jörn

-- 
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-- Howard Aiken quoted by Ken Iverson quoted by Jim Horning quoted by
   Raph Levien, 1979
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