linux-kernel - Re: [RFC PATCH v2 0/4] Add support for LZ4-compressed kernel

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Date:	Wed, 27 Feb 2013 22:23:58 +0900
From:	Kyungsik Lee <kyungsik.lee@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"Markus F.X.J. Oberhumer" <markus@...rhumer.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org, x86@...nel.org,
	celinux-dev@...ts.celinuxforum.org,
	Nicolas Pitre <nico@...xnic.net>,
	Nitin Gupta <nitingupta910@...il.com>,
	Richard Purdie <rpurdie@...nedhand.com>,
	Josh Triplett <josh@...htriplett.org>,
	Joe Millenbach <jmillenbach@...il.com>,
	David Sterba <dsterba@...e.cz>,
	Richard Cochran <richardcochran@...il.com>,
	Albin Tonnerre <albin.tonnerre@...e-electrons.com>,
	Egon Alter <egon.alter@....net>, hyojun.im@....com,
	chan.jeong@....com, raphael.andy.lee@...il.com
Subject: Re: [RFC PATCH v2 0/4] Add support for LZ4-compressed kernel

On Wed, Feb 27, 2013 at 09:51:39AM +0000, Russell King - ARM Linux wrote:
> On Wed, Feb 27, 2013 at 04:36:47PM +0900, Kyungsik Lee wrote:
> > Compiler: Linaro ARM gcc 4.6.2
> > 2. ARMv7, 1.7GHz based board
> >    Kernel: linux 3.7
> >    Uncompressed Kernel Size: 14MB
> >          Compressed Size  Decompression Speed
> >     LZO  6.0MB            34.1MB/s            Old
> >          ----------------------------------------
> >          6.0MB            34.7MB/s            New
> >          6.0MB            52.2MB/s(UA)
> >     =============================================
> >     LZ4  6.5MB            86.7MB/s
> > UA: Unaligned memory Access support
> 
> That is pretty conclusive - it shows an 8% increase in image size vs a
> 66% increase in decompression speed.  It will take a _lot_ to offset
> that increase in decompression speed.
> 
> So, what I think is that yes, we should accept LZ4 and drop LZO from
> the kernel - the "fast but may not be small" compression title has
> clearly been taken by LZ4.

I have read the comments regarding how many compressors the kernel
should support and understand that it can not support all the
compressors available.

However, I don't think that LZO can be replaced by LZ4 in all the
cases. The benchmark above shows only about improved decompression
speed.

Thanks,
Kyungsik

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