Re: [PATCH v3 0/8] Add support for ZSTD-compressed kernel and initramfs

Sedat Dilek
2020-04-01T09:50:54Z

On Wed, Apr 1, 2020 at 4:52 AM Nick Terrell <terrelln@fb.com> wrote:
>
>
>
> > On Mar 31, 2020, at 8:11 AM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > On Tue, Mar 31, 2020 at 6:15 AM Nick Terrell <terrelln@fb.com> wrote:
> >
> > [...]
> >
> >>> Do you plan to push this for Linux v5.7?
> >>
> >> I hope that it will be accepted. From my point of view this patch set is
> >> ready for merge, except for the maximum window size increase
> >> requested by Petr.
> >>
> >
> > Hi Nick,
> >
> > thanks for your answer.
> >
> > Did you send out a pull-request already?
>
> I haven’t sent out a pull request. If that is something that I need to
> do, or if it makes the process easier for a maintainer to merge then
> I can do that.
>

[ CC Stephen Rothwell (maintainer of Linux-next) ]

Hi Nick,

as Adam pointed out it might be good to ask "Stephen Rothwell"
<sfr@canb.auug.org.au>
to include your Git tree into linux-next. Stephen will give you some
informations about that.

> > Can you point me to that request or patch of Petr?
> > Is it relevant or optional for the pull-request?
>
> The patches from Petr are a parallel implementation of initramfs
> decompression and are available here [0]. They support initramfs
> compression well, but are missing some pieces for correct and
> performant zstd kernel decompression. Namely the equivalent of
> patch 6 in this series to increase ZO_z_extra_bytes, the
> performance fix in patch 1 that switches memcpy() to
> __builtin_memcpy(), and the decompress_single() function in patch 3.
>
> Without those changes a very compressible kernel may fail to
> decompress successfully, and will be corrupted. And the performance
> is about 4x worse on x86_64. My patches took 70 ms to decompress vs
> 318 ms with Petr’s. See the detailed comparison here [1].
>

Thanks for version 4 of your patchset and these clarifications.

I will try zstd-v4.

Regards,
- Sedat -

> >>> Feel free to add credits for the whole series:
> >>>
> >>> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> >>
> >> Thanks for testing the patch set Sedat!
> >>
> >
> > I have re-tested zstd-v3 patchset with Linux version 5.6 final and
> > Clang/LLD version 10.0.0 final (from Debian/unstable repository).
> >
> > Is it possible to mention that there might distro-specific changes
> > needed to initramfs-handling?
> > For Debian you are welcome to include below Link [1].
> > Not sure I will send/ask to/on the debian-kernel mailing list in this topic.
>
> I don’t expect any distro specific changes are required to continue operating
> as-is. However, if a distro wanted to switch to a zstd compressed initramfs
> they would need to update their toolchain to compress with zstd.
>
> > Thanks and bonne chance.
> >
> > Regards,
> > - Sedat -
> >
> > [1] LINK: https://lore.kernel.org/lkml/CA+icZUXCn2an9aNDrm+-eneSAOyGibz0W1xYhwkA5k3B3U-5vQ@mail.gmail.com/
>
> [0] https://lkml.org/lkml/2020/3/16/461
> [1] https://lkml.org/lkml/2020/3/31/1573
>