Date: Thu, 22 Dec 2005 09:37:04 -0800
From: Marc Singer <elf@buici.com>
To: Axel Kittenberger <axel.kernel@kittenberger.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Possible Bootloader Optimization in inflate (get rid of unnecessary 32k Window)
Message-ID: <20051222173704.GB23411@buici.com>
References: <200512221352.23393.axel.kernel@kittenberger.net>
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On Thu, Dec 22, 2005 at 01:52:23PM +0100, Axel Kittenberger wrote:
> Hello, Whom do I talk to about acceptance of Patches in the Bootloader?
> 
> I have seen, and coded once some time ago for priv. uses, do infalte the 
> gziped linux kernel at boottime in "arch/i386/boot/compressed/misc.c" and " 
> windowlib/inflate.c" the deflation algorthimn uses a 32k backtrack window. 
> Whenever it is full, it copies it .... into the memory. 
> 
> While this window makes a lot of sense in an userspace application like 
> gunzip, it does not make a lot sense in the bootloader. As userspace 
> application the window is flushed to a file when full. The bootloader 
> "flushes" it to memory (copies it in memory). That 1 time copy of the whole 
> kernel can be optimized away, since we do not keep track of a window since 
> the inflater can read what it has written right in the computer memory, while 
> it unpacks the kernel.
> 
> What would the optimization be worth? 
> * A faster uncompressing of the kernel, since a total 1-time memcopy of the 
> whole kernel is been optimized away.

Have you timed this operation?  I would predict that the time to copy
the kernel is nominal as compared the the time taken to perform the
decompression.
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