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

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Message-ID: <20130227163118.GB17833@n2100.arm.linux.org.uk>
Date:	Wed, 27 Feb 2013 16:31:18 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Joe Perches <joe@...ches.com>
Cc:	Peter Korsgaard <jacmet@...site.dk>,
	Nicolas Pitre <nico@...xnic.net>,
	"Markus F.X.J. Oberhumer" <markus@...rhumer.com>,
	Kyungsik Lee <kyungsik.lee@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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,
	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 07:49:12AM -0800, Joe Perches wrote:
> On Wed, 2013-02-27 at 09:56 +0000, Russell King - ARM Linux wrote:
> > On Tue, Feb 26, 2013 at 05:40:34PM -0800, Joe Perches wrote:
> > > On Tue, 2013-02-26 at 22:10 +0000, Russell King - ARM Linux wrote:
> > > > So... for a selected kernel version of a particular size, can we please
> > > > have a comparison between the new LZO code and this LZ4 code, so that
> > > > we can see whether it's worth updating the LZO code or replacing the
> > > > LZO code with LZ4?
> > > 
> > > How could it be questionable that it's worth updating the LZO code?
> > 
> > Please read the comments against the previous posting of these patches
> > where I first stated this argument - and with agreement from those
> > following the thread.  The thread started on 26 Jan 2013.  Thanks.
> 
> https://lkml.org/lkml/2013/1/29/145
> 
> I did not and do not see significant value in
> adding LZ4 given Markus' LZO improvements.

Sorry, a 66% increase in decompression speed over the updated LZO code
isn't "significant value" ?

I'm curious - what in your mind qualifies "significant value" ?

Maybe "significant value" is a patch which buggily involves converting
all those "<n>" printk format strings in assembly files to KERN_* macros,
thereby breaking those strings because you've not paid attention to what
.asciz means?  (Yes, I've just cleaned that crap up after you...)

> Why would the LZO code not be updated?

I'm not saying that the LZO code should not be updated.  I'm saying that
the kernel boot time decompressor is not a play ground for an ever
increasing number of "my favourite compression method" crap.  We don't
need four, five or even six compression methods there.  We just need
three - a "fast but large", "small but slow" and "all round popular
medium".
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