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

[Manuel Ebner <manuelebnerli@mailbox.org>]

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

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

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
> ...