Hi Olivier,
2017-01-23, Olivier Matz:
Before this patch, the management of dependencies between directories
had several issues:
- the generation of .depdirs, done at configuration is slow: it can take
more than one minute on some slow targets (usually ~10s on a standard
PC).
Indeed, on a Qualcomm development board where disk I/O is quite slow:
$ git describe
v17.02-rc1-3-g61207d014fc9
$ time make config T=arm64-armv8a-linuxapp-gcc
real 1m4.308s
- for instance, it is possible to expressed a dependency like:
s/expressed/express/
- we cannot use "make -d" for debug, because the output of make is used
for the generation of .depdirs.
That is really annoying when debugging makefiles.
After applying this patch:
$ git am mk-optimize-directory-dependencies.patch
Applying: mk: optimize directory dependencies
$ rm -rf build/
$ time make config T=arm64-armv8a-linuxapp-gcc
real 0m0.111s
Almost 600 times faster than before!
I prefer this solution to the one proposed by Ferruh (which is
interesting but requires to run parallel make). Here is a test with the
other patch:
$ git am mk-parallelize-make-config.patch
Applying: mk: parallelize make config
$ rm -rf build/
$ grep -c processor /proc/cpuinfo
24
$ time make config T=arm64-armv8a-linuxapp-gcc -j24
real 0m11.253s
Here only 6 times faster than before, even when using 24 parallel
processes.
Tested-by: Robin Jarry <robin.ja...@6wind.com>
