On Fri, Sep 9, 2011 at 1:22 PM, Lubos Lunak <l.lu...@suse.cz> wrote: > So if ccache has 0% hit ratio, there is 17% overhead in this specific case. > With 100% hit ratio, 73% is saved. That, if my math is right, means at least > 19% ccache hit ratio is required for breaking even.
I'm am gathering numbers, in the mean time http://tinderbox.libreoffice.org/MASTER/status.html give me some good data about the ccache hit. by looking at the time it take for each build iteration... most of them show that the hit ration is almost always very very high (90%+), unless some commit touch a commonly included header. Now granted, once we can reliably do incremental build, the question of the effectiveness of ccache will be much more acute. presumable incremental build only try to compile stuff that _need_ to be compiled and therefore should be a ccache miss... so with perfect incremental build the ccache hit should be 0% when that is true, we could indeed change the default for ccache to disable.... FYI: my ccachs -s for my MacOSX buildbot is n_th@tpamac ~/.ssh $ccache -s cache directory /Volumes/ccache_ramdisk cache hit (direct) 481347 cache hit (preprocessed) 19049 cache miss 28588 called for link 25314 multiple source files 102 compile failed 8524 preprocessor error 4318 bad compiler arguments 1768 unsupported source language 408 autoconf compile/link 35802 unsupported compiler option 60295 no input file 7446 files in cache 43163 cache size 1.8 Gbytes max cache size 2.3 Gbytes so a hit ration of 94.6% (481347 + 19049) / (481347 + 19049 + 25588) (note that cache had been wiped out about 2 days ago due to an IPL of the box -- the cache is in ramdisk, so it does not survive a reboot) Norbert _______________________________________________ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
