From: Ingo Molnar <mingo@kernel.org>
Date: Tue, 1 Oct 2013 15:17:22 +0000 (+0200)
Subject: tools/perf/build: Speed up the final link
X-Git-Tag: omap-for-v3.13/fixes-for-merge-window-take2~41^2~28^2~127
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c9404c6650d8f58ce8cf98d4c5581fc5c9e37faf;p=pandora-kernel.git

tools/perf/build: Speed up the final link

libtraceevent.a and liblk.a rules have always-missed dependencies,
which causes python.so to be relinked at every build attempt - even
if none of the affected code changes.

This slows down re-builds unnecessarily, by adding more than a second
to the build time:

  comet:~/tip/tools/perf> time make

  ...

    SUBDIR /fast/mingo/tip/tools/lib/lk/
    make[1]: `liblk.a' is up to date.
    SUBDIR /fast/mingo/tip/tools/lib/traceevent/
    LINK perf
    GEN python/perf.so

  real    0m1.701s
  user    0m1.338s
  sys     0m0.301s

Add the (trivial) dependencies to not force a re-link.

This speeds up an empty re-build enormously:

  comet:~/tip/tools/perf> time make

  ...

  real    0m0.207s
  user    0m0.134s
  sys     0m0.028s

[ This adds some coupling between the build dependencies of
  libtraceevent and liblk - but until those stay relatively
  simple this should not be an issue. ]

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-wvmlrurufuk6mo1ovtNigguT@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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