linux-kernel - Re: [PATCH] initramfs: restore default compression behaviour

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Date:   Thu, 12 Mar 2020 05:12:28 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH] initramfs: restore default compression behaviour

Hi Eugeniy.

On Wed, Mar 11, 2020 at 7:22 PM Eugeniy Paltsev
<Eugeniy.Paltsev@...opsys.com> wrote:
>
> Even though INITRAMFS_SOURCE kconfig option isn't set in most of
> defconfigs it is used (set) extensively by various build systems.
> Commit f26661e12765 ("initramfs: make initramfs compression choice
> non-optional") has changed default compression mode. Previously we
> compress initramfs using available compression algorithm. Now
> we don't use any compression at all by default.
> It significantly increases the image size in case of build system
> chooses embedded initramfs. Initially I faced with this issue while
> using buildroot.
>
> As of today it's not possible to set preferred compression mode
> in target defconfig as this option depends on INITRAMFS_SOURCE
> being set.
> Modification of build systems doesn't look like good option in this
> case as it requires to check against kernel version when setting
> compression mode. The reason for this is that kconfig options
> describing compression mode was renamed (in same patch series)

Which commit?

I do not remember the renaming of kconfig options
with this regard.



> so
> we are not able to simply enable one option for old and new kernels.
>
> Given that I propose to use GZIP as default here instead of NO
> compression. It should be used only when available but given that
> gzip is enabled by default it looks like good enough choice.



Another solution would be to move
INITRAMFS_COMPRESSION_NONE to the end of the choice menu.

The default of the choice menu is the first visible entry.

GZIP if RD_GZIP is defined, BZIP2 if RD_BZIP2 is defined ...



> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>  usr/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/usr/Kconfig b/usr/Kconfig
> index bdf5bbd40727..690ef9020819 100644
> --- a/usr/Kconfig
> +++ b/usr/Kconfig
> @@ -102,6 +102,7 @@ config RD_LZ4
>
>  choice
>         prompt "Built-in initramfs compression mode"
> +       default INITRAMFS_COMPRESSION_GZIP if RD_GZIP
>         depends on INITRAMFS_SOURCE != ""
>         help
>           This option allows you to decide by which algorithm the builtin
> --
> 2.21.1
>


-- 
Best Regards
Masahiro Yamada