linux-kernel - Re: [PATCH bpf-next v2] kbuild: Remove debug info from kallsyms linking

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Message-ID: <9dd690e8-868d-d463-6b85-14270fdcc210@iogearbox.net>
Date:   Wed, 4 Mar 2020 19:40:05 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Kees Cook <keescook@...omium.org>, bpf@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        linux-kbuild@...r.kernel.org, andriin@...com
Subject: Re: [PATCH bpf-next v2] kbuild: Remove debug info from kallsyms
 linking

On 3/4/20 3:18 AM, Kees Cook wrote:
> When CONFIG_DEBUG_INFO is enabled, the two kallsyms linking steps spend
> time collecting and writing the dwarf sections to the temporary output
> files. kallsyms does not need this information, and leaving it off
> halves their linking time. This is especially noticeable without
> CONFIG_DEBUG_INFO_REDUCED. The BTF linking stage, however, does still
> need those details.
> 
> Refactor the BTF and kallsyms generation stages slightly for more
> regularized temporary names. Skip debug during kallsyms links.
> Additionally move "info BTF" to the correct place since commit
> 8959e39272d6 ("kbuild: Parameterize kallsyms generation and correct
> reporting"), which added "info LD ..." to vmlinux_link calls.
> 
> For a full debug info build with BTF, my link time goes from 1m06s to
> 0m54s, saving about 12 seconds, or 18%.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Acked-by: Andrii Nakryiko <andriin@...com>

Applied, thanks!