Date:   Thu, 23 Feb 2023 13:16:04 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     =?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>
Cc:     linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
        Masahiro Yamada <masahiroy@kernel.org>, kernel-dev@igalia.com,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>
Subject: Re: [PATCH] kbuild: modinst: Enable multithread xz compression
Message-ID: <Y/fJhOME2OAPWILK@dev-arch.thelio-3990X>
References: <20230223001607.95523-1-andrealmeid@igalia.com>
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On Wed, Feb 22, 2023 at 09:16:07PM -0300, Andr? Almeida wrote:
> As it's done for zstd compression, enable multithread compression for
> xz to speed up module installation.
> 
> Signed-off-by: Andr? Almeida <andrealmeid@igalia.com>

This seems reasonable to me.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

If for some reason Masahiro does not want to take this, you could set
XZ_OPT=-T0 in your build environment, which should accomplish the same
thing.

> ---
> 
> On my setup xz is a bottleneck during module installation. Here are the
> numbers to install it in a local directory, before and after this patch:
> 
> $ time make INSTALL_MOD_PATH=/home/tonyk/codes/.kernel_deploy/ modules_install -j16
> Executed in  100.08 secs
> 
> $ time make INSTALL_MOD_PATH=/home/tonyk/codes/.kernel_deploy/ modules_install -j16
> Executed in   28.60 secs
> ---
>  scripts/Makefile.modinst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
> index 4815a8e32227..28dcc523d2ee 100644
> --- a/scripts/Makefile.modinst
> +++ b/scripts/Makefile.modinst
> @@ -99,7 +99,7 @@ endif
>  quiet_cmd_gzip = GZIP    $@
>        cmd_gzip = $(KGZIP) -n -f $<
>  quiet_cmd_xz = XZ      $@
> -      cmd_xz = $(XZ) --lzma2=dict=2MiB -f $<
> +      cmd_xz = $(XZ) --lzma2=dict=2MiB -f -T0 $<
>  quiet_cmd_zstd = ZSTD    $@
>        cmd_zstd = $(ZSTD) -T0 --rm -f -q $<
>  
> -- 
> 2.39.2
>