https://bugs.kde.org/show_bug.cgi?id=490651
--- Comment #8 from Philippe Waroquiers <philippe.waroqui...@skynet.be> --- (In reply to Sam James from comment #7) > The reproduction instructions you used seem mixed. If you compile with > `make` (implicit -j1), then it's essentially the same, as GCC won't > parallelise. > > If you run with `make -jN`, then GCC will automatically use the jobserver > make created and consume slots for LTO parallelisation I always used make -j20 install (the "time" truncated the string, but the full command was given at the beginning of the comment). But in any case, even if parallelism was not used, I got around slightly less than 6 minutes of config/make -j20/install for both builds (not the 35 minutes you observed). > (https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto): > > You can also specify -flto=jobserver to use GNU make’s job server mode to > > determine the number of parallel jobs. This is useful when the Makefile > > calling GCC is already executing in parallel. You must prepend a ‘+’ to the > > command recipe in the parent Makefile for this to work. This option likely > > only works if MAKE is GNU make. Even without the option value, GCC tries to > > automatically detect a running GNU make’s job server. > > I suspect this explains the discrepancy. As explained above, make -j20 without tests used slightly than 6 minutes for both lto builds, and make with tests around 22 and 23 minutes. So, I do not observe 35 minutes nor a significant difference between the 2 lto builds. Might of course be heavily influenced by the CPU used (I used a AMD Ryzen Threadripper PRO 5975WX 32-Cores) -- You are receiving this mail because: You are watching all bug changes.
