linux-kernel - Re: [PATCH 1/2] init/Kconfig: add option to disable kernel compression

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Date:	Fri, 15 Nov 2013 17:57:50 +0100
From:	Christian Ruppert <christian.ruppert@...lis.com>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	Pavel Roskin <proski@....org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Sam Ravnborg <sam@...nborg.org>, Noam Camus <noamc@...hip.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 1/2] init/Kconfig: add option to disable kernel
 compression

On Thu, Nov 14, 2013 at 03:51:22PM +0530, Vineet Gupta wrote:
> +CC Sam for Kconfig wisdom
> 
> On 11/14/2013 02:08 PM, Christian Ruppert wrote:
> > Some ARC users say they can boot faster with without kernel compression.
> > This probably depends on things like the FLASH chip they use etc.
> > 
> > Until now, kernel compression can only be disabled by removing "select
> > HAVE_<compression>" lines from the architecture Kconfig.  So add the
> > Kconfig logic to permit disabling of kernel compression.
> > 
> > Signed-off-by: Christian Ruppert <christian.ruppert@...lis.com>
> > ---
> >  arch/arc/Kconfig |  2 ++
> >  init/Kconfig     | 12 +++++++++++-
> >  2 files changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> > index 91dbb27..3991f03 100644
> > --- a/arch/arc/Kconfig
> > +++ b/arch/arc/Kconfig
> > @@ -21,6 +21,8 @@ config ARC
> >  	select HAVE_ARCH_KGDB
> >  	select HAVE_ARCH_TRACEHOOK
> >  	select HAVE_IOREMAP_PROT
> > +	select HAVE_KERNEL_UNCOMPRESSED
> > +	select HAVE_KERNEL_GZIP
> 
> Fine.
> 
> >  	select HAVE_KPROBES
> >  	select HAVE_KRETPROBES
> >  	select HAVE_MEMBLOCK
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 3ecd8a1..b1a6f92 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -97,6 +97,9 @@ config LOCALVERSION_AUTO
> >  
> >  	  which is done within the script "scripts/setlocalversion".)
> >  
> > +config HAVE_KERNEL_UNCOMPRESSED
> > +        bool
> > +
> 
> This is good to avoid perturbing other arches.
> 
> >  config HAVE_KERNEL_GZIP
> >  	bool
> >  
> > @@ -118,7 +121,6 @@ config HAVE_KERNEL_LZ4
> >  choice
> >  	prompt "Kernel compression mode"
> >  	default KERNEL_GZIP
> > -	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
> >  	help
> >  	  The linux kernel is a kind of self-extracting executable.
> >  	  Several compression algorithms are available, which differ
> > @@ -137,6 +139,14 @@ choice
> >  
> >  	  If in doubt, select 'gzip'
> >  
> > +config KERNEL_UNCOMPRESSED
> > +	bool "No compression"
> > +	depends on HAVE_KERNEL_UNCOMPRESSED || ! ( HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 )
> > +	help
> > +	  No compression at all. The kernel is huge but the compression and
> > +	  decompression times are zero.
> > +	  This is usually not what you want.
> > +
> >  config KERNEL_GZIP
> >  	bool "Gzip"
> >  	depends on HAVE_KERNEL_GZIP
> > 
> 
> How about doing this part slightly differently (simpler IMO).
> We add uncompressed as just another category rather than being a special case.
> 
> Indicative diff against current mainline code
> 
>  choice
>         prompt "Kernel compression mode"
>         default KERNEL_GZIP
> -       depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA ||
> HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
> +       depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA ||
> HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
> 
> 
> +config KERNEL_UNCOMPRESSED
> +       bool "No compression"
> +       depends on HAVE_KERNEL_UNCOMPRESSED
> +

Good Idea. I fixed this and sent the updated patch directly in reply to
H. Peter's revert patch to avoid too much patch ping-pong:
http://www.spinics.net/lists/kernel/msg1636397.html

Greetings,
  Christian
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