Re: [PATCH v10 4/8] usr: add support for zstd compressed initramfs

[Sedat Dilek]

On Tue, Aug 4, 2020 at 8:52 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
> Hi Nick,
>
> On Thu, Jul 30, 2020 at 9:13 PM Nick Terrell <nickrterrell@xxxxxxxxx> wrote:
> > From: Nick Terrell <terrelln@xxxxxx>
> >
> > * 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@xxxxxxxxxxxx>
> > Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
> > Signed-off-by: Nick Terrell <terrelln@xxxxxx>
>
> 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.
>

Hi Geert,

you are right - for new stuff it should be "default n".

What I am missing - still - is a note - that your user-space should
have the correct bits to support zstd-initramfs.
Unsure where to place such an information.

If you send a patch for above feel free to add my:

Reviewed-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>

Thanks.

Regards,
- Sedat -

[1] https://bugs.debian.org/955469

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> 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