ccache cache miss slow down compilation a lot

Question

Just started using ccache based on this tutorial and so far I like it. However, caches miss are being extremely slow. Here are my results :

Regular clean build without ccache : 1m40s
First build with ccache : 4m36s
Second build with ccache : 30s

I’m not sure where to start debugging. The performance page (https://ccache.samba.org/performance.html) mentions how complexity of the make file can slow down compilation, but in this context I use Xcode so call of ccache should be relatively quick. I was expecting some performance decrease, but not this much!

There are my current settings using version 3.2.5 :

export CCACHE_MAXSIZE=3G
export CCACHE_HARDLINK=true
export CCACHE_SLOPPINESS=pch_defines,file_macro,time_macros,include_file_mtime,include_file_ctime,file_stat_matches

Note that I do use a pch, if that changes something.

Answer 1

You may run command "ccache -s" to see the statistics.

And from experiments at the end of this ccache bug thread https://github.com/ccache/ccache/issues/54, try reducing the parallel cores compiler used may help, file locking from multiple processes may be the root cause.