On Sat, Nov 28, 2020 at 7:05 AM Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Nov 27, 2020 at 1:53 PM Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > 33.68% cc1plus > > So a third of the time is the _single_ invocation of cc1plus, which > happens from scrips/gcc-plugin.sh doing that > > $HOSTCC -c -x c++ -std=gnu++98 - -fsyntax-only > > thing. Which is purely to verify that plugins work. > > Ugh. > > Emese - I'm talking to myself while I'm looking at why "make > allmodconfig" is so unbearably slow. This is part of it. > > Linus If you do 'make allmodconfig' from the clean source tree, some logs are displayed. If you do that once again, no logs, which means no recompilation of the 'conf' binary. Of course, GNU Make evaluates some recipes due to the FORCE, but the costs are quite small. As for the cc1plus cost, I got a similar result. Running scripts/gcc-plugin.sh directly took me 0.5 sec, which is a fourth of the allmodconfig run-time. Actually, I did not know this shell script was so expensive to run... I also added Kees to CC. Even if we are able to manage this script somehow, Kconfig invocation still takes more than 1 sec due to the current design. masahiro@grover:~/workspace/linux$ make mrproper masahiro@grover:~/workspace/linux$ time make allmodconfig HOSTCC scripts/basic/fixdep HOSTCC scripts/kconfig/conf.o HOSTCC scripts/kconfig/confdata.o HOSTCC scripts/kconfig/expr.o LEX scripts/kconfig/lexer.lex.c YACC scripts/kconfig/parser.tab.[ch] HOSTCC scripts/kconfig/lexer.lex.o HOSTCC scripts/kconfig/parser.tab.o HOSTCC scripts/kconfig/preprocess.o HOSTCC scripts/kconfig/symbol.o HOSTCC scripts/kconfig/util.o HOSTLD scripts/kconfig/conf # # configuration written to .config # real 0m4.415s user 0m3.686s sys 0m0.763s masahiro@grover:~/workspace/linux$ time make allmodconfig # # No change to .config # real 0m2.041s user 0m1.564s sys 0m0.519s masahiro@grover:~/workspace/linux$ export HOSTCC=gcc masahiro@grover:~/workspace/linux$ time scripts/gcc-plugin.sh gcc real 0m0.560s user 0m0.512s sys 0m0.048s -- Best Regards Masahiro Yamada
