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Date: Wed, 27 Feb 2013 11:20:53 +0100
From: Johannes Stezenbach <js@sig21.net>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Kyungsik Lee <kyungsik.lee@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Markus F.X.J. Oberhumer" <markus@oberhumer.com>,
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        Egon Alter <egon.alter@gmx.net>, hyojun.im@lge.com, chan.jeong@lge.com,
        raphael.andy.lee@gmail.com
Subject: Re: [RFC PATCH v2 0/4] Add support for LZ4-compressed kernel
Message-ID: <20130227102053.GA24274@sig21.net>
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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 think LZO may be used by squashfs, jffs2 and btrfs, thus you
cannot drop it without breaking on disk storage formats.

Johannes