On Fri, May 31, 2019 at 4:43 PM Tadeus Prastowo <tadeus.prastowo@xxxxxxxx> wrote: > > On Wed, May 29, 2019 at 12:37 PM Tadeus Prastowo > <tadeus.prastowo@xxxxxxxx> wrote: > > > > On Tue, May 28, 2019 at 10:00 PM Stefan Ring <stefanrin@xxxxxxxxx> wrote: > > > > > > On Mon, May 27, 2019 at 1:49 AM Tadeus Prastowo > > > <tadeus.prastowo@xxxxxxxx> wrote: > > > > Once debuild is done, I installed the aforementioned DEB files and > > > > found out that the installed /usr/bin/g++-9 still compiles faster as > > > > before. So, I have failed to identify the factor in the PPA build > > > > process that makes the resulting compiler faster than mine, which was > > > > built from the release tarball using configure & make. Any idea how > > > > to find the factor that results in a faster compiler? Is it really > > > > the build process or the way the resulting compiler is installed that > > > > gives the speed up? For example, does symbol stripping have any > > > > effect (I tried already to strip all symbols out of the executables > > > > found in my GCC-9 installation with `strip -s' but to no avail)? > > > > Perhaps some compiler libraries are installed in a particular way in > > > > Ubuntu? > > > > > > I guess the Ubuntu package uses "make profiledbootstrap", which you > > > don’t get (IIRC) when just issuing "make". > > > > Yes, that is true, but that did not ring my bell. Thank you very much > > for ringing the bell for me, quoting > > https://gcc.gnu.org/install/build.html: > > It is possible to use profile feedback to optimize the compiler > > itself. This should result in a faster compiler binary. Experiments > > done on x86 using gcc 3.3 showed approximately 7 percent speedup on > > compiling C programs. To bootstrap the compiler with profile feedback, > > use make profiledbootstrap. > > > > I will give it a try and report it back. > > Yes, it is very likely that the use of `make profiledbootstrap' is the > main factor that boosts the compilation speed of vanilla GCC 9. > > I say ``very likely'' because compiling vanilla GCC 9 using `make > profiledbootstrap' results in a missing Makefile error as detailed in > this thread: https://gcc.gnu.org/ml/gcc-help/2019-05/msg00137.html > > However, forcing the PPA build not to use `profiledbootstrap' by > editing the `debian/rules.defs' file results in DEB packages whose > g++-9 runs slower by almost 9%. To clarify: it runs slower by almost 9% than the vanilla GCC 9 whose runtime was reported in the start of this thread. The first trial gives: real 6m9.464s user 0m27.593s sys 0m2.933s The second trial gives: real 6m29.064s user 0m28.635s sys 0m3.161s > So, I hypothesize that if the vanilla > GCC 9 were successful, it would also run faster by almost 15%. > > Thank you very much for your kind help, Stefan. > > -- > Best regards, > Tadeus
