Re: [PATCH v3 20/20] kbuild: compress the kernel with pigz if available

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Fri, Sep 18, 2026 at 04:27:39PM +0200, Manuel Ebner wrote:
> Hi Lorenzo,
>
> On Thu, 2026-09-17 at 17:06 +0100, Lorenzo Stoakes (ARM) wrote:
> > The gzip step of a kernel build is very lengthy, especially for larger
> > builds such as allmodconfig.
> >
> > ...
> >
> > Whole build, 128-thread Threadripper 9980X, best of N runs:
> >
> >                                          before   after     delta
> >                                          -------------------------------
> >   x86 defconfig, touch mm/vma.c, gcc        7.7s     6.0s     -1.7s (-22%)
> >   x86 defconfig, touch mm/vma.c, clang      6.9s     5.4s     -1.5s (-21%)
> >   x86 defconfig, clean, gcc                28.2s    26.3s     -1.8s (-6%)
> >   x86 defconfig, clean, clang              28.7s    27.2s     -1.5s (-5%)
> >   x86 allmodconfig, touch mm/vma.c, gcc    23.7s    15.4s     -8.3s (-35%)
> >   x86 allmodconfig, touch mm/vma.c, clang  22.5s    15.6s     -7.0s (-31%)
> >   x86 allmodconfig, clean, gcc            294.1s   278.6s     -15.5s (-5%)
> >   x86 allmodconfig, clean, clang          283.9s   266.8s     -17.1s (-6%)
>
> That's good to hear.

:)

>
>
> > Suggested-by: Kees Cook <kees@kernel.org>
> > Link: https://zlib.net/pigz/
> > Assisted-by: LLM
> > Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> > ---
> >  Documentation/kbuild/kbuild.rst   | 17 +++++++++++++++++
> >  Documentation/process/changes.rst |  8 ++++++++
> >  Makefile                          |  5 ++++-
> >  kernel/Makefile                   |  6 +++++-
> >  scripts/Makefile.lib              |  4 ++--
>
> Please add a line to
> scripts/ver_linux

Ack, done for v4!

>
> >  scripts/jobserver-exec            |  3 ++-
> >  tools/lib/python/jobserver.py     | 13 +++++++++++++
> >  7 files changed, 51 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
> > index 5a9013bacfb7..e71a692a559a 100644
> > --- a/Documentation/kbuild/kbuild.rst
> > +++ b/Documentation/kbuild/kbuild.rst
> > @@ -110,6 +110,23 @@ HOSTLDLIBS
> >  ----------
> >  Additional libraries to link against when building host programs.
> >
> > +KGZIP
> > +-----
> > +The gzip program used for compressed modules, packaging and the embedded
>
> Could you also add gzip to changes.rst and ver_linux while you are at it?
> Rest looks good to me.

I'd rather leave that out of this series tbh, if I listed it then I have to
choose a minimum version that and feels out of scope.

One for a follow-up?

> Reviewed-by: Manuel Ebner <manuelebnerli@mailbox.org>

Thanks!

>
> Thanks
>  Manuel
>
> > +kernel configuration. Defaults to gzip.
> > +
> > +KPGZIP
> > +------
> > +The gzip program used for the compressed kernel image. Defaults to pigz (a
> > +parallel implementation of gzip), run under scripts/jobserver-exec so that it
> > +uses the job slots make has free, if pigz is installed, otherwise to
> > +``KGZIP``. Set ``KPGZIP=`` on the make command line to use another program.
> > +
> > +KBZIP2, KLZOP, LZMA, LZ4, XZ, ZSTD
> > +----------------------------------
> > +The compressor programs for the other formats. Each defaults to the program
> > +of the same name.
> > +
> >  .. _userkbuildflags:
> >
> >  USERCFLAGS
> > diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> > index 0aa232b117b5..28f2ca63318e 100644
> > --- a/Documentation/process/changes.rst
> > +++ b/Documentation/process/changes.rst
> > @@ -55,6 +55,7 @@ nfs-utils              1.0.5            showmount --version
>
> + gzip
>
> >  openssl & libcrypto    1.0.0            openssl version
> >  pahole                 1.26             pahole --version
> >  pcmciautils            004              pccardctl -V
> > +pigz (optional)        2.4              pigz --version
> >  PPP                    2.4.0            pppd --version
> >  procps                 3.2.0            ps --version
> >  Python                 3.9.x            python3 --version
> > @@ -206,6 +207,13 @@ GNU AWK
> >  GNU AWK is needed if you want kernel builds to generate address range data for
> >  builtin modules (CONFIG_BUILTIN_MODULE_RANGES).
> >
> > +pigz (optional)
> > +---------------
> > +
> > +pigz is a parallel implementation of gzip. If it is installed the compressed
> > +kernel image is produced with it rather than with gzip, see ``KPGZIP`` in
> > +Documentation/kbuild/kbuild.rst.
> > +
> >  System utilities
> >  ****************
> >
> > diff --git a/Makefile b/Makefile
> > ...
>

--
Cheers, Lorenzo