I've discovered that there is too small buffer size for IO in ccache: 16k or 10k (in hash_fd, copy_fd, copy_file).
I did simple fix and run several tests (on mac osx) trying to recompile chromium. (Of course there was 100% cache hit). Results (pay your attention to sys time): 16k real 8m47.043s user 47m43.881s sys 13m29.614s 32k real 8m35.696s user 47m27.329s sys 12m23.814s 64k real 8m33.496s user 47m31.393s sys 12m0.532s 128k real 8m31.473s user 47m45.633s sys 11m53.050s 256k real 8m30.719s user 47m54.551s sys 11m51.810s 512k real 8m39.989s user 48m7.429s sys 12m11.997s 1m real 8m44.547s user 48m20.203s sys 12m36.895s 2m real 8m48.912s user 48m34.397s sys 12m59.308s I'm going to make an PR at github. _______________________________________________ ccache mailing list firstname.lastname@example.org https://lists.samba.org/mailman/listinfo/ccache