On Mon, 2015-02-09 at 23:36 +0000, Richard Purdie wrote: > On Mon, 2015-02-09 at 13:05 +0000, Richard Purdie wrote: > > In an effort to get to the bottom of this I made a git bisection, timing > > the performance of building xz with make -j1 using each different > > libtool. > > > > The issues come down to this commit: > > > > http://git.savannah.gnu.org/cgit/libtool.git/commit/?id=0a42997c6032b9550a009a271552e811bfbcc430 > > > > libtool: rewritten over funclib.sh instead of general.m4sh. > > > > Before that, I get a time of about 20s, after it, 39s. If I cherry-pick > > in the fix in master mentioned above, I get 27s. > > > > So whilst things are better (thanks!), the above change is still causing > > a regression in the performance somewhere else. Any ideas what else in > > that rather large change may be causing this? > > To further narrow this down, of the changes in the above commit, the > problem appears to be in the changes to the option parsing code. I've > included the diff below which if I apply on top of the above, I get the > speed back. I've left the func_split_short_opt/func_split_long_opt code > in there but that is worth a tiny part of the speed, the issues are > around the addition of the func_options call. > > As yet I don't know enough about the code in question to know why this > is an issue but traces of libtool show a lot more looping in code to do > with argument parsing and quoting.
To be more specific, if I take my "good" libtool and add: func_options_prep ${1+"$@"} it slows the build down by 0.5s on a 21s build. If I look at func_options_prep and comment out the line: func_run_hooks func_options_prep ${1+"$@"} I get the 0.5s back. In func_run_hooks, if I comment: func_quote_for_eval ${1+"$@"} func_run_hooks_result=$func_quote_for_eval_result I get the 0.5s back. The issue is all the quoting of the various return values through all this looping. It doesn't appear to be hitting the printf/sed in func_quote_for_eval which would be an obvious slow path, its just the shear number of loops run through with the commandline arguments. The change adds a number of calls to func_run_hooks, not just the single test case I have above and all combined, it slows things down significantly. So is there a way we can change things so its not calling func_quote_for_eval all the time with all the looping that entails? Cheers, Richard _______________________________________________ https://lists.gnu.org/mailman/listinfo/libtool