Re: [PATCH] lib: xz: add support for bcj filters

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Falco Hyfing <hyfinglists@gmail.com>,
	barebox <barebox@lists.infradead.org>
Subject: Re: [PATCH] lib: xz: add support for bcj filters
Date: Wed, 22 Feb 2017 12:34:48 +0100	[thread overview]
Message-ID: <20170222113448.vwd6xnj5zspfhdlk@pengutronix.de> (raw)
In-Reply-To: <CAGm1_ktS6tyZPCMC1_HcP5e64=kCyO8=mz-S4hobgBxx6rVkiQ@mail.gmail.com>

On Wed, Feb 22, 2017 at 11:35:46AM +0100, Yegor Yefremov wrote:
> On Wed, Feb 22, 2017 at 11:21 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> > On Wed, Feb 22, 2017 at 11:10:36AM +0100, Yegor Yefremov wrote:
> >> On Wed, Feb 22, 2017 at 11:03 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> >> > On Wed, Feb 22, 2017 at 09:15:36AM +0100, Yegor Yefremov wrote:
> >> >> On Wed, Feb 22, 2017 at 5:29 AM, Jean-Christophe PLAGNIOL-VILLARD
> >> >> <plagnioj@jcrosoft.com> wrote:
> >> >> >
> >> >> >> On Feb 21, 2017, at 10:47 PM, yegorslists@googlemail.com wrote:
> >> >> >>
> >> >> >> From: Yegor Yefremov <yegorslists@googlemail.com>
> >> >> >>
> >> >> >> Add missing configuration options for various bcj filters. Without
> >> >> >> these options the lib/xz/xz_dec_bcj.c file will be compiled, but all
> >> >> >> filters will be disabled.
> >> >> >>
> >> >> >> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
> >> >> >> ---
> >> >> >> lib/Kconfig | 28 ++++++++++++++++++++++++++++
> >> >> >> 1 file changed, 28 insertions(+)
> >> >> >>
> >> >> >> diff --git a/lib/Kconfig b/lib/Kconfig
> >> >> >> index f9f25bdef..83dd8e0a4 100644
> >> >> >> --- a/lib/Kconfig
> >> >> >> +++ b/lib/Kconfig
> >> >> >> @@ -22,6 +22,34 @@ config XZ_DECOMPRESS
> >> >> >>       bool "include xz uncompression support"
> >> >> >>       select UNCOMPRESS
> >> >> >>
> >> >> >> +if XZ_DECOMPRESS
> >> >> >> +
> >> >> >> +config XZ_DEC_X86
> >> >> >> +        bool "x86 BCJ filter decoder"
> >> >> >> +        default y
> >> >> > this need to be ARCH dependant
> >> >>
> >> >> Why? In Linux kernel it is not arch dependent, because AFAIK it
> >> >> describes only compression particularities. This way you can extract
> >> >> sqaushfs images on your ARM machine, that were compressed on SPARK
> >> >> etc.
> >> >
> >> > So xz uses the Sparc bcj filter even when compressing ARM binaries? That
> >> > doesn't sound very mature to me.
> >>
> >> This is just an xz command line option. So it is completely in the
> >> user responsibility.
> >
> > I see. What's the default for this option? The architecture xz is
> > running on?
> >
> > Otherwise we could do a:
> >
> > config XZ_DEC_ARM
> >         bool "ARM BCJ filter decoder"
> >         default y if ARCH_ARM
> >
> > On the other hand I'm not sure if the potential image size gain for
> > disabling the unused bcj filters is even worth thinking about the
> > problem...
> 
> My barebox images without filters:
> 
> 4668516 barebox
> 640752 barebox.bin
> 
> with all filters:
> 
> 4679592 barebox
> 642632 barebox.bin

Ok, so not worth discussing about. Size concerned people should disable
xz support ;)

Sascha

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