linux-kernel - [PATCH 0/4] kbuild: optimize output directory creation

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Date:   Fri, 10 Nov 2017 00:41:13 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Douglas Anderson <dianders@...omium.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <mmarek@...e.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...hat.com>
Subject: [PATCH 0/4] kbuild: optimize output directory creation


I looked into the build scripts, focusing on "mkdir" optimization.

With this series, I succeeded in speeding up the incremental build
with O= option.

The following is the result of "time make O=foo",
where "foo" is the output directory that has already been built.

Before:

real	0m8.322s
user	0m4.324s
sys	0m1.220s

After:

real	0m6.989s
user	0m4.168s
sys	0m1.080s

3/4 gave the biggest impact.



Masahiro Yamada (4):
  kbuild: create directory for make cache only when necessary
  kbuild: remove redundant $(wildcard ...) for cmd_files calculation
  kbuild: create object directories simpler and faster
  kbuild: optimize object directory creation for incremental build

 Makefile                     |  3 +--
 arch/x86/entry/vdso/Makefile |  4 ----
 scripts/Kbuild.include       | 13 +++++++++----
 scripts/Makefile.build       | 23 ++++++++++++-----------
 scripts/Makefile.headersinst |  3 +--
 scripts/Makefile.host        | 11 -----------
 scripts/Makefile.lib         |  5 -----
 scripts/Makefile.modpost     |  3 +--
 8 files changed, 24 insertions(+), 41 deletions(-)

-- 
2.7.4