linux-kernel - Re: [PATCH] kbuild: speed up checksyscalls.sh

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Message-ID: <CAK7LNARcvevZMEj2P=3dss3_qfeGd-tjVU4_tZ3efu4c+CmfXw@mail.gmail.com>
Date:   Sat, 10 Jun 2017 01:16:34 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Michal Marek <mmarek@...e.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH] kbuild: speed up checksyscalls.sh

2017-06-01 23:57 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
> checksyscalls.sh is run at every "make" run while building the kernel,
> even if no files have changed. I looked at where we spend time in
> a trivial empty rebuild and found checksyscalls.sh to be a source
> of noticeable overhead, as it spawns a lot of child processes just
> to call 'cat' copying from stdin to stdout, once for each of the
> over 400 x86 syscalls.
>
> Using a shell-builtin (echo) instead of the external command gives
> us a 13x speedup:
>
>     Before                 After
> real    0m1.018s       real     0m0.077s
> user    0m0.068s       user     0m0.048s
> sys     0m0.156s       sys      0m0.024s
>
> The time it took to rebuild a single file on my machine dropped
> from 5.5 seconds to 4.5 seconds.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied to linux-kbuild/kbuild.  Thanks!




-- 
Best Regards
Masahiro Yamada