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Bug#940887: Integrate ZSTD patches *Kernel compression: add ZSTD, remove LZMA1 and BZIP2*

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  Bug#940887: Integrate ZSTD patches *Kernel compression: add ZSTD, remove LZMA1 and BZIP2* Paul Menzel <pmenzel@molgen.mpg.de> - 2019-09-21 16:10 +0200
    Bug#940887: Integrate ZSTD patches *Kernel compression: add ZSTD, remove LZMA1 and BZIP2* Adam Borowski <kilobyte@angband.pl> - 2019-09-22 17:10 +0200

#65149 — Bug#940887: Integrate ZSTD patches *Kernel compression: add ZSTD, remove LZMA1 and BZIP2*

Package: src:linux
Version: 5.2.9-2
Severity: wishlist


Dear Linux folks,


It’d be awesome, if you applied Adam’s and Nick’s patches for ZSTD 
support [1] to the Debian kernel, so users can test those early for the 
next Debian release.

Here is the cover letter text:

> Hi!
> As new compressors get invented, they tend to find their way into the
> kernel, yet we never prune superseded ones.  It's time to do so.
> 
> In particular, BZIP2 is drastically slower than other compressors we
> have, even when they achieve smaller sizes.  It takes more memory, too.
> And, BZIP2 is not used anywhere else in the kernel -- just for booting
> the kernel itself and the initrd.  Thus, we can drop it from the tree
> completely, making Linus happier by around 900 lines.
> 
> LZMA1 is redundant with XZ (LZMA2), and unlike the latter, it uses its own
> copy of code that's not shared with anything else (some drivers use XZ).
> Let's drop it as well.  Some bootloaders can use it thus let's keep the
> Kconfig option, but I left no piece of code inside the kernel itself.
> 
> On the other hand, Nick Terrell has a couple of patches adding ZSTD support
> (using code already in use in multiple pieces around the kernel).  ZSTD is
> strong and fast, obsoleting all mid-range compressors.  As the removal of
> BZIP2 and LZMA1 would be hopelessly entangled with this addition, I'm
> resending Nick's patches here.  I've been booting using them since Oct'17
> on amd64 (kernel+initrd), armhf and arm64 (initrd) without issues, other
> folks tested various other architectures as well.
> 
> Thus, I'd recommend people to use:
> * XZ for most machines
> * ZSTD where speed is important
> * maaaaybe LZ4 is some special cases
> (grub and u-boot are ridiculously slow at reading, making fast but weak
> decompressors a net loss.  On the other hand, XZ decompresses pretty fast
> but is very slow at compress time, making ZSTD preferred for rapid devel
> cycles.)
> 
> * we can't get rid of GZIP in foreseable future
> * LZO is obsolete but is used elsewhere in the kernel
> 
> Total:
>  69 files changed, 518 insertions(+), 1785 deletions(-)
> 
> Not sure whose tree this patchset should go through.  I'm also not sure
> how finely split into commits you want the arch bits be; I included
> defconfig bits all together, yet separated code changes per-arch.
> 
> 
> Meow!


Kind regards,

Paul


[1]: https://lore.kernel.org/patchwork/cover/1009317/

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#65152

On Sat, Sep 21, 2019 at 04:00:55PM +0200, Paul Menzel wrote:
> Dear Linux folks,
> 
> 
> It’d be awesome, if you applied Adam’s and Nick’s patches for ZSTD support
> [1] to the Debian kernel, so users can test those early for the next Debian
> release.

> [1]: https://lore.kernel.org/patchwork/cover/1009317/

While adding the first part, ZSTD initrd and image, might be plausible,
cleanup like the rest of the patchset is right out.

I guess it's a time to resubmit the patchset upstream... except that we're
right in the middle of the merge window.


Meow!
-- 
⢀⣴⠾⠻⢶⣦⠀ A MAP07 (Dead Simple) raspberry tincture recipe: 0.5l 95% alcohol,
⣾⠁⢠⠒⠀⣿⡁ 1kg raspberries, 0.4kg sugar; put into a big jar for 1 month.
⢿⡄⠘⠷⠚⠋⠀ Filter out and throw away the fruits (can dump them into a cake,
⠈⠳⣄⠀⠀⠀⠀ etc), let the drink age at least 3-6 months.

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