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>
c9404c6650