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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 4 Aug 2020 08:52:38 +0200
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Subject: Re: [PATCH v10 4/8] usr: add support for zstd compressed initramfs
To:     Nick Terrell <nickrterrell@gmail.com>
Cc:     Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Chris Mason <clm@fb.com>,
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        "the arch/x86 maintainers" <x86@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Petr Malat <oss@malat.biz>, Kees Cook <keescook@chromium.org>,
        Kernel Team <Kernel-team@fb.com>,
        Adam Borowski <kilobyte@angband.pl>,
        Patrick Williams <patrickw3@fb.com>, rmikey@fb.com,
        Ingo Molnar <mingo@kernel.org>,
        Patrick Williams <patrick@stwcx.xyz>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Norbert Lange <nolange79@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alex Xu <alex_y_xu@yahoo.ca>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nick Terrell <terrelln@fb.com>
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Hi Nick,

On Thu, Jul 30, 2020 at 9:13 PM Nick Terrell <nickrterrell@gmail.com> wrote:
> From: Nick Terrell <terrelln@fb.com>
>
> * Add support for a zstd compressed initramfs.
> * Add compression for compressing built-in initramfs with zstd.
>
> I have tested this patch by boot testing with buildroot and QEMU.
> Specifically, I booted the kernel with both a zstd and gzip compressed
> initramfs, both built into the kernel and separate. I ensured that the
> correct compression algorithm was used. I tested on arm, aarch64, i386,
> and x86_64.
>
> This patch has been tested in production on aarch64 and x86_64 devices.
>
> Additionally, I have performance measurements from internal use in
> production. On an aarch64 device we saw 19 second boot time improvement
> from switching from lzma to zstd (27 seconds to 8 seconds). On an x86_64
> device we saw a 9 second boot time reduction from switching from xz to
> zstd.
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> Signed-off-by: Nick Terrell <terrelln@fb.com>

Thanks for your patch, which is now commit a30d8a39f0571425 ("usr: Add
support for zstd compressed initramfs").

> --- a/usr/Kconfig
> +++ b/usr/Kconfig
> @@ -100,6 +100,15 @@ config RD_LZ4
>           Support loading of a LZ4 encoded initial ramdisk or cpio buffer
>           If unsure, say N.
>
> +config RD_ZSTD
> +       bool "Support initial ramdisk/ramfs compressed using ZSTD"
> +       default y
> +       depends on BLK_DEV_INITRD
> +       select DECOMPRESS_ZSTD
> +       help
> +         Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
> +         If unsure, say N.

I'm aware you copied this from the other entries, but IMHO "default y",
and "If unsure, say N" are not a good combination.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds